Type: Imbuement
Strategy: With a duration of only three rounds and an effect of only increasing the character's actions like saving throws and to hit chances by 1, this spell is pretty much a waste of time. If you ever find you can't perform an action, it could prove useful to use this spell to compensate. However, we have never found a time when the spell could help. Spells like Melf's acid arrow and mirror image will be a much better use of your spell slots.
Importance: Low
Melf's Acid Arrow
Type: Missile damage
Strategy: Aside from the spiffy name, the spell has some nice effects. First, on impact, 2d4 points of damage are inflicted. From there, the acid deals 2d4 points of damage per round, with the number of rounds increasing with the levels of the caster. In other words, the damage is good, and the acid will stay dealing more damage over time. Though at later levels, the spell is resisted, it is very good in the early portions of the game and especially useful for taking out trolls and disrupting other mages.
Importance: High
Mirror image should be the first spell any mage casts in most battles.
Mirror Image
Type: Defense
Strategy: This spell creates multiple mirrored images of the caster, with each image absorbing a hit. In combat, this allows the mage some leeway to maneuver and helps him greatly. Who can refuse hits that deal no damage? Also, the number of images increases with each level, so the long-term value is high.
Importance: Vital
Power Word: Sleep
Type: Hindrance
Strategy: The spell will affect only enemies with less than 20 hit points. Suffice it to say, you will never need to sleep anything with less than 20 hit points - you will find almost no enemies at that low a level.
Importance: None
Ray of Enfeeblement
Type: Hindrance
Strategy: Lowering the strength of the enemy to five, this spell works wonders when it isn't resisted. However, other than a few situations, most difficult enemies will have saving throws high enough to resist it. But, for the few times that they don't, keep a copy memorized. If you find yourself in an impossible battle, try casting this spell to see if it gets off. If it does, it will make your day.
Importance: Moderate
Resist Fear
Type: Defense
Strategy: Since this spell does not counteract magically invoked fear, it is practically useless. Since fear no longer occurs as a result of a tough battle as often as in Baldur's Gate, you will rarely have a use for this.
Importance: Low
Stinking Cloud
Type: Hindrance
Strategy: Though this spell will affect friends and foe alike, this, like many others, works well when cast at a distance from your party. Once the enemies are unconscious, a barrage of missiles will take them out one by one. Though resisted by higher-level enemies, this works well into the game.
Importance: Moderate
Strength
Type: Imbuement
Strategy: Raising your character's strength to 18/50, this will let the character hit slightly harder. Overall, the effects are negligible and barely help since most fighters (of all types) are already at, near, or higher than 18/50.
Importance: Low
Vocalize
Type: Dispel
Strategy: Curing silence is easily done with dispel magic. Use that instead and save a spell slot. Since your mage cannot actually cast when silenced, he cannot even cure himself anyway.
Importance: Low
Web
Type: Hindrance
Strategy: This is another great spell to keep the masses off you while you fight a few enemies at a time. Web will create a large area of effect that will stop enemies from moving unless they make a save at -2. The -2 save means that almost every creature will have a difficult time resisting this. This is a spell to have in your memory banks 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 best cast at a distance unless you're willing to risk your own party.
Importance: High
