Paladins gain their first divine spell at level 9 and max out their spell ability at level 20, at which point they have access to three spells in each spell level 1-4

Level 1

Armor of Faith

Type: Defense
Strategy: Absorbing a portion of all damage done to the caster and increasing with the level of the caster, this spell is a great, basic armor spell. Though it will taper off, it is useful and stays so. Cast it before any major battle.
Importance: High

Bless

Type: Imbuement
Strategy: Affecting all creatures in a certain area with bonus to luck and dice rolls, bless is another acceptable buff-up spell. The dice rolls will make a small difference in your combat abilities, and it's worth casting if you have the time before major battles.
Importance: Moderate

Command Word: Die

Type: Hindrance
Strategy: This spell renders a creature unconscious for one round. The spell, with no saving throw, gives you one free round to do as you will before the creature returns to normal. A lot can happen in one round.
Importance: High

Cure Light Wounds

Type: Heal
Strategy: Cast this spell on a hurt party member. It heals one to eight points of damage. For Baldur's Gate II, that amount is negligible. However, it is useful to cut down on the number of hours spent resting, so if you find no other worthwhile spells, fill level 1 up with this.
Importance: Low

Detect Evil

Type: Detection
Strategy: Use this spell to find which creatures are evil in the area. When cast, a list will be made of all evil creatures. It's useful if you missed any enemies in a dungeon, and it's useful to determine motives and alignment.
Importance: Moderate

Doom

Type: Hindrance
Strategy: Giving a +2 THACO to the target, this spell actually manages to lower the target's combat abilities a noticeably small amount. The -2 to all general rolls, however, will help with spells cast in the future on the target as well as your ability to hit the target. In general, it's a nifty, if small, spell.
Importance: Moderate

Entangle

Type: Hindrance - druid only
Strategy: This is another great spell to keep the masses off of you while you fight just a few enemies at a time. Entangle will create a large area of effect that will stop enemies from moving unless they make a save at +2. This is a spell to have in your memory as you go into almost any battle, but beware - you can get your own party stuck, too. So, this is another one of those spells to cast at a distance, unless you want to take the risk.
Importance: Moderate

Magical Stone

Type: Missile damage
Strategy: A great principal level 1 damage spell, magical stone creates a projectile that does one to four points of damage to the target. The one to four points of damage is irresistible and quite good for a level 1 spell. Obviously, one to four points of damage is not great, but at level 1, it is nice for a small punch.
Importance: Moderate

Protection From Evil

Type: Defense
Strategy: This spell will become increasingly more useful as the game progresses. Not only is it a must for summoning minions, it will also protect you against many demons found in the later parts of the game. One particular battle comes to mind where there are hordes of demons, and casting this spell will let you turn the tide of battle from an impossible situation to an easy victory. However, if you happen to have a class like a paladin in your party, he will come with plenty of these spells as special abilities, so you shouldn't bother memorizing it.
Importance: High or low, depending on party makeup

Remove Fear

Type: Cure, heal, and dispel
Strategy: If your party members are afflicted by natural or magically induced fear, this spell will cure them. Also, it will help them resist it for the duration of the spell. Since fear is a common effect of spells in Baldur's Gate II, remove fear is actually quite useful.
Importance: Moderate

Sanctuary

Type: Defense
Strategy: When sanctuary is cast, the target can no longer take any offensive or defensive action without destroying the spell. A wonderful spell if you find your priest low in hit points, it will give him time to rest up, heal, and rejoin the battle without dying.
Importance: Moderate

Shillelagh

Type: Summoning
Strategy: This spell summons a magical club for the caster. In Baldur's Gate II, you will have a better weapon than this will summon, so it is pointless and, actually, detrimental.
Importance: None

Level 2

Aid

Type: Imbuement
Strategy: The aid effect is nice, but the additional 1d8 hit points are pretty much negligible to anyone but a mage. It is advised that you simply stay with bless, which is one spell rank lower.
Importance: Low

Barkskin

Type: Defense
Strategy: With effects that increase as you level up, barkskin begins useful and stays useful. Eventually lowering your base armor class to two, this spell will usually be one step ahead of your ability to find better equipment. It's definitely one of the better lower-level armor spells.
Importance: High

Chant

Type: Imbuement, hindrance
Strategy: Raising all party rolls by one, and lowering all enemy rolls by one, chant is simple but pretty effective for a level 2 spell, having the same general effectiveness as a double-bless spell.
Importance: Moderate

Charm Person or Mammal

Type: Charm - druid only
Strategy: This spell grants control of any one humanoid or mammal enemy to the player for five rounds. Toward the end of the original Baldur's Gate, most creatures resisted the charm series of spells. The same problem is present here in Baldur's Gate II, so most often, the spell will never get off successfully. However, keeping one copy of the spell memorized is advised for earlier portions of the game for those times when you do run into a person or mammal susceptible to charm.
Importance: Moderate

Draw Upon Holy Might

Type: Imbuement
Strategy: Gaining power as you level up, this spell will increase strength, constitution, and dexterity by one point for every three levels of the caster. In the later portions of the game, this spell can take your stats to godlike numbers and will give substantial bonuses. As you progress, this spell becomes increasingly important and will play a key role in making your priest one of your best all-around party members.
Importance: Vital

Find Traps

Type: Other
Strategy: Just like the thief's ability, this spell will let you locate traps. If you have a thief in your party (and you should), this spell is useless. If you don't, this spell is a must for dungeons.
Importance: Low or high, depending on party makeup

Flame Blade

Type: Summoning
Strategy: This spell summons a blade of flame (1d4+4) for the caster to use; this spell is especially good against trolls. As its name suggests, the blade is made of flame and will hence kill trolls. Otherwise, its damage and bonuses against the undead are actually quite nice and may be better than the weapon you have for the first bits of the game.
Importance: Moderate

Goodberry

Type: Cure, heal, and summoning - druid only
Strategy: Healing one point of damage, goodberries aren't so tasty (excuse the pun). Truly one point of damage is as inconsequential as it gets. Don't bother with this spell.
Importance: None

Hold Person

Type: Hindrance
Strategy: This spell freezes one humanoid creature in place, letting you do anything to it without consequence. Early in the game, when the spell is not resisted, it can work wonders again humanoid enemies. Later in the game, its use tapers off.
Importance: Moderate

Know Alignment

Type: Other
Strategy: If you ever find yourself in a situation where you are not sure whether to trust or not to trust those with whom you are dealing, casting this spell will answer it. However, it is usually more beneficial to follow through and trust, even if you know it's a trap, as the result can lead to hefty treasure, experience, and even new party members.
Importance: Low

Resistance to Fire and Cold

Type: Defense
Strategy: If you find yourself under cold or fire attacks from spells, traps, or anything else, casting this will absorb 50 percent of all cold and fire damage. This happens very infrequently in Baldur's Gate II and is only usable under select circumstances.
Importance: Low

Silence, 15-foot Radius

Type: Hindrance
Strategy: Casting silence will prevent enemy spellcasters from casting. A most efficient spell, but it's resisted most of the time. If you are not too far into the game, keep a copy memorized and see if it will affect anyone. If so, the cast will be well worth your time.
Importance: Moderate

Slow Poison

Type: Cure, Heal
Strategy: In Baldur's Gate II, most poisons will require a more potent spell to neutralize the poison. However, this spell will slow the poison. Use it only as a backup if all other poison cures are unavailable.
Importance: Low

Spiritual Hammer

Type: Summoning
Strategy: Summoning a magical hammer that will be +2 or +3, it is entirely up to you whether it is worth it or not. If your weapon is not as good, casting spiritual hammer will help. If your weapon is better, there is no point. You will most likely have a better weapon soon enough.
Importance: Low

Level 3

Animate Dead

Type: Summoning
Strategy: Letting more undead be summoned with each level, this spell becomes quite powerful, especially when used with hindrance spells. Since skeletons are immune to most spells like confusion and stinking cloud, it is a good idea to cast any of those hindrance spells, then move in on the skeletons while picking off the remaining enemies with long-range weaponry. Skeletons are particularly good against mind flayers, since they are not affected by their spells.
Importance: High

Call Lightning

Type: Missile damage - druid only
Strategy: This spells calls down one bolt of lightning that deals two to eight +1d8 points of damage per turn per level of experience. At higher levels, a very good amount of damage can be done, but it is often resisted. Also, the fact that this spell can only be cast outside makes it nearly impossible to use.
Importance: Low

Cure Disease

Type: Cure, heal
Strategy: If a party member is affected by disease, blindness, or deafness, casting this spell will cure him. Since this will happen often, this spell is very useful.
Importance: High

Cure Medium Wounds

Type: Heal
Strategy: Cast this spell on a hurt party member. This spell heals 14 points of damage. For Baldur's Gate II, that amount is small. However, it is useful to cut down on hours of rest, so if you find no better spells, fill up level 2 with this.
Importance: Low

Dispel Magic

Type: Dispel
Strategy: Most spell-induced ailments and magic effects can be cured with a cast of dispel magic. Since the level of the caster in relation to the level of the spell being cured is important, have your higher-level characters use this. Though this spell is very important to have around, paladins get some casts of this as a special ability. If you have one in your party, this can relieve some of the stress off the spellcaster.
Importance: High or low, depending on party makeup

Glyph of Warding

Type: Defense
Strategy: Used to protect a door or chest from entry, glyph of warding is of no use in Baldur's Gate II, as NPCs do not touch doors or chests.
Importance: None

Hold Animal

Type: Hindrance - druid only
Strategy: This spell freezes one animal-type creature in place, letting you do anything to it without consequence. Early in the game, when the spell is not resisted, it could work wonders against animal enemies, but there are none. Later in the game, when you begin to run into animals of some consequence, its effectiveness tapers off, making it all but useless in Baldur's Gate II.
Importance: Low

Holy Smite

Type: Area damage
Strategy: Dealing one to four points of damage per level of the caster to all evil creatures in the area of effect with a save for half, this spell will do tremendous amounts of damage at higher levels. This spell works especially well against the undead, sometimes killing a whole pack in a single casting. Otherwise, your group is easy prey to any pack of evil creatures.
Importance: High

Invisibility Purge

Type: Dispel
Strategy: If your party ever comes under attack from any type of invisible creature, casting this spell will force it back into visibility. However, on your journey, you will rarely face invisible creatures, and when you do, they will become barely visible when they attack you. Unless they have used greater invisibility, you can attack them from there (though your party will attack at a penalty). Also, you can easily cast dispel to rid the creature of the invisibility if needed.
Importance: Low

Miscast Magic

Type: Hindrance
Strategy: Forcing an 80 percent chance of failure on the spellcasting ability of the target, this spell works wonders at disrupting chain casting. One problem is that it is often resisted. Another is that it only lasts one turn. However, if it gets off, this causes hell for any spellcaster's casting.

Protection from Fire

Type: Defense
Strategy: If you find yourself under fire attacks from spells, traps, or anything else, casting this will absorb 80 percent of all fire damage taken. This happens very infrequently in Baldur's Gate II and can only be used in a select few situations.
Importance: Low

Remove Curse

Type: Cure, heal
Strategy: If you ever equip a cursed item, this spell will cure you of its effects and let you get rid of it. Churches will also perform this for a small amount of gold.
Importance: Moderate

Remove Paralysis

Type: Cure
Strategy: If you find yourself under paralysis, casting this will remove its effect. This happens very infrequently in Baldur's Gate II and can only be used in a select few situations. Churches will also perform this for a small amount of gold.
Importance: Moderate

Rigid Thinking

Type: Hindrance
Strategy: This is a nice spell if you are getting overwhelmed by low-level enemies and need time to deal with a few enemies at a time. Rigid thinking sends the target wandering, confused, or randomly attacking and will give you time to hit the other creatures or the target while it can't hit back. Remember, though, that when the spell wears off, the creature will be back in action. The monster gets a save, so it can resist. However, there are higher-level fear spells that can take effect on high-level creatures, get resisted less, and do more. For the level, though, the spell works acceptably on those lower-level creatures.
Importance: Moderate

Strength of One

Type: Imbuement
Strategy: Giving the entire party 18/76 strength, this can help and hurt. First, all your party members can gain strength to 18/76 if it is less than that level. If their strength is higher, though, they lose strength down to 18/76. If the majority of your party is weak, this spell can work wonders for battling. You will, however, find girdles like the girdle of hill giant strength that will help out where you need it most, so that you don't need to keep casting this spell. Remember, once you have said girdles, this spell will actually hurt.
Importance: Moderate

Summon Insects

Type: Area damage, hindrance - druid only
Strategy: Rather an all-in-one spell, this spell summons a swarm of insects that deals one damage every two seconds for seven rounds. Also, the target suffers a -2 penalty to attack rolls and a +2 penalty to armor class. Most importantly, this spell also confers a 50 percent chance of spell failure on the target. Though the damage is negligible, all the other effects add up to make this a decent spell. However, the spell will become resisted quickly. So use it while it lasts, then move on.
Importance: Moderate

Unholy Blight

Type: Area Damage
Strategy: See holy smite. This spell works exactly the same way, except that the damage is against good creatures. If you are an evil character and plan on killing shopkeepers and other good creatures, this spell could serve you well. However, most will play the game by the rules and be fighting evil. So, it is of little use to most.
Importance: Low

Zone of Sweet Air

Type: Dispel
Strategy: This spell clears the area of all vapor-based effects like cloudkill and grease. Since enemy wizards have a lovely knack of casting these types of things all the time, this spell is extremely useful. Keep a copy or two memorized and dispel those vapor area affect spells as soon as you can. It will save you immeasurable amounts of health and frustration.
Importance: High

Level 4

Animal Summoning I

Type: Summoning
Strategy: Like the mage series of monster-summoning spells, this summons spell animals to fight for the caster. It does, however, summon fairly low hit point creatures that do almost no damage. Though some of the later summon spells are great to cast for creatures that absorb damage, this won't do much of anything and is just a waste of time.
Importance: Low

Call Woodland Beings

Type: Summoning - druid only
Strategy: Call woodland beings summons a nymph to help the party. Though nymphs make fairly lackluster fighters, they have a few spells at their disposal and can heal, confuse, and dominate enemies. If you need more spells, she may be worth summoning, but by the middle of Baldur's Gate II, the nymph's spells do almost nothing. Since she can't fight well, she loses any importance and is quickly not worth casting.
Importance: Low

Cause Serious Wounds

Type: Touch damage
Strategy: Since priests can wear most armor, they can naturally double as fighters. So, though touch damage spells are abysmal for mages, they serve to boost the already competent fighting abilities of the priest. For these spells, you must wait until you are attacking an enemy worth casting this spell on. Then, once you are out of harm's way, and the target is concentrating on attacking another party member, cast this spell. Once cast, you have two rounds to successfully hit the enemy. Once you do, this spell will deal 17 points of damage to it (with no saving throw). If you don't hit it, though, the spell will be wasted. So, make sure your priest has good enough weapons, and you are in a position to hit. All in all, if used correctly, cause serious wounds, like the rest of the line of priest touch spells, is extraordinary.
Importance: High

Cloak of Fear

Type: Hindrance
Strategy: Like the mage spell horror in effect, cloak of fear creates a magical cloak around the caster that will instill fear within a three-foot radius of the caster. This is a nice spell if you are getting overwhelmed by low-level enemies and need time to deal with a few of the enemies at a time, as it will give you time to hit them when they can't hit back. Since the cloak moves with the caster, this spell will also help alleviate the pressure on the front lines. Remember, though, that when the spell wears off, the terrified creatures will be back in action. The monsters get a save, so do not expect them all to be affected. However, there are higher-level fear spells that can take effect on higher-level creatures, get resisted less, and have a longer effect. For the level, though, the spell works acceptably on those lower-level creatures.
Importance: Moderate

Cure Serious Wounds

Type: Cure, heal
Strategy: Cast it on a hurt party member. This spell heals 17 points of damage. For Baldur's Gate II, that amount is acceptable and can be used outside of combat to heal the party back to full strength. However, the spell is also useful to cut down on hours of rest, so if you find no other spells, fill up level 4 with it.
Importance: High

Death Ward

Type: Defense
Strategy: This spell grants the target protection from spells like disintegrate, power word: kill, death spell, and finger of death. Since higher-level mages use these types of necromantic spells often, death ward becomes increasingly needed at higher levels. Once you start seeing these types of spells cast on you, you may want to keep a copy of death ward memorized to protect your most fragile party member. The downfall is that it only affects one creature, so it is impractical to defend the entire party.
Importance: Moderate

Defensive Harmony

Type: Defense
Strategy: Granting a +2 bonus to the armor class of all party members within ten feet of the target, defensive harmony can turn good fighters into untouchable instruments of death. A two-point bonus to armor class should not be underestimated and will help at all times in the game. Since this spell affects an area, one cast will benefit the entire party. Overall, it's very useful in any and all battles.
Importance: High

Farsight

Type: Other
Strategy: This spell is identical to the wizard spell of the same name. Farsight is a spell that often comes in handy, revealing a portion of the map and clearing the fog of war. This will let you easily scope out an area and memorize and cast needed spells before barging in. It's very useful for the more difficult areas of the game.
Importance: High

Free Action

Type: Cure, heal
Strategy: Working in much the same way as dispel magic, free action dispels all movement-hindering spells. That includes those that dispel but will not free, like web and paralysis. Overall, one copy of this spell must be memorized for the times for when these spells are cast on your party. In general, though dispel magic will clear many spells, it will not clear everything. Free action is one of the spells that pick up what's left.
Importance: High
Holy Power

Type: Imbuement
Strategy: Giving the caster 18/00 strength, an increase to THAC0, and additional hit points, holy power will help your priest act a bit more like a fighter. If you already have high strength, though, the main use of this spell has been negated. So, if you need the help, use it. Otherwise, go for a spell that will bestow a few more bonuses.
Importance: Low

Lesser Restoration

Type: Cure, heal
Strategy: The wonder spell for vampire hunting, lesser restoration will annul most energy-drain effects like drain level. Since these are extremely common when hunting vampires, and hunting vampires is itself very common, a copy of this should be memorized at all times.
Importance: High

Mental Domination

Type: Charm
Strategy: This spell lets the caster gain control of any creature that fails its saving throw. Otherwise, the spell acts strategically much like any other charm spell, such as charm person or mammal. In this case, though, the difference is that any creature can be charmed. Also, this spell is resisted much less and works incredibly well against most low- to mid-level creatures.
Importance: Moderate

Negative Plane Protection

Type: Defense
Strategy: Bestowing partial protection to undead and spells like drain level, negative plane protection only works when fighting creatures like vampires. Though the though of never worrying about drain level is nice, this spell only affects one creature. Since vampires have a nasty habit of attacking everyone, it serves little purpose.
Importance: Low

Neutralize Poison

Type: Cure, heal
Strategy: In Baldur's Gate II, most poisons will require a potent spell to neutralize them, and this spell is your best bet. Not only will it dispel the poison, it will heal a few hit points. It will even cure blindness and deafness. It's a four-in-one spell and comes in handy all the time.
Importance: High

Poison

Type: Missile damage
Strategy: Dealing continuous damage that gets more potent and has a longer duration as the caster levels up, poison packs a good punch when it is cast successfully. However, poison seems to be one of the easiest spells to resist. So, unless you use a magic resistance decreasing spell, poison can't do anything at all. If you do use it, try to find a very potent damage-over-time spell that is great to start a battle with, then follow it up with other damaging spells.
Importance: Moderate

Protection from Evil, 10-foot Radius

Type: Defense
Strategy: Like a normal protection from evil spell, this spell will become increasingly more useful. The difference between the two is that this one's range is ten feet instead of one. Not only is it a must for summoning minions, it will protect you against many demons found in the later parts of the game. One particular battle comes to mind where there are hordes of demons, and casting this spell will let you turn the tide of battle from an impossible situation to an easy victory. However, if you happen to have a class like a paladin in your party, he will come with plenty of normal protection from evil spells as his special ability. So, if you value the range boost, this spell is worth it. Otherwise, stick to the normal paladin ability.
Importance: Low or high, depending on party makeup

Protection from Lightning

Type: Defense
Strategy: Working like all other protection spells, protection from lightning confers immunity to all electric damage. It's useful if you are up against a mage who likes lightning bolt, or if you find yourself in an area with lightning traps, but usually, it's is of no help at all.
Importance: Low