If you're planning on putting your lightsabers to heavy use in KOTOR, then you'll want to boost your strength score to a decent rank when you create your character. (Maybe; see the dexterity section below for a more detailed look at the way strength works with lightsabers and Jedi characters.) The modifier that you gain from strength is applied to the attack roll and damage of a melee weapon, meaning that a character with high strength will find it both easier to hit an opponent and easier to inflict large amounts of damage. If you plan to focus on ranged weaponry, however, you shouldn't need many points in strength; there are no strength requirements for any items in KOTOR, and since your inventory is unlimited in size, you don't need to have a high strength to carry loot around.
Dexterity is likely going to be the primary attribute for most players, since a high dexterity modifier affects your attack rolls with both ranged weapons and, oddly enough, lightsabers. That bonus is also applied to your defense, making you more agile in battle and thus less likely to be shot or hit with an enemy weapon. Your defense modifier may be reduced or even eliminated if you wear heavier suits of armor that restrict your ability to dodge, so you should be sure to check your defense before and after you put on new threads to ensure that they actually benefit you. The dexterity modifier is also applied as a bonus to your reflex saving throws, allowing you to more easily escape serious injury from situations that call for quick moves, such as a nearby explosion.
The balancing of dexterity and strength will be critical for lightsaber-intensive characters. In most cases, the attack roll of a melee weapon is determined in part by the Strength modifier, but with lightsabers, it appears that the game uses the higher of the strength and dexterity modifiers to add to the attack roll, so that if your character has a dexterity of 16, and a strength of 14, then the attack roll modifier for a lightsaber would be the +3 from the dexterity. The strength modifier would still be applied to the damage rolled, however.
Where this becomes important is in the consideration that many of the Jedi Force powers require your character to not be wearing armor. While the many varieties of Jedi robes offer some light protection, and some Force powers themselves will boost your defense, your character will still generally lag far behind your other Jedi party members in terms of defense, since they will almost always join your party with two levels of the Jedi Sense feat in their belt.
You can probably see where we're going with this: if your Jedi character has a high strength, but low dexterity, he or she will deal quite a bit of damage, but will either have to wear armor to survive combat, and forgo the use of the many useful powers that are armor-restricted, or wade into combat with a low defense. If you possess a high dexterity, but a low strength stat, then you'll be able to go a bit longer in combat without having to resort to the cure power or medpacs, but will deal less damage on the whole than a character with high strength.
Want a hint? Go with dexterity. You may not be a melee powerhouse in the earliest portions of the game, but you'll be able to use any ranged weapon with ease, even without a focus feat, and you'll have the advantage of a very high defense when wearing light armor. You can still pump your strength score at character creation, perhaps by under-boosting constitution and making the difference in vitality back later on with the toughness feat. If you want very specific advice, a 16/16 split between strength and dexterity at character creation makes Taris quite survivable for most characters, and when you become a Jedi, you'll be able to cast off your armor for the Jedi robes without any qualms, especially if you devote the first two attribute additions to dexterity.
Also note that if you plan to become a Jedi guardian, you'll be able to use the lightsaber specialization feat. Since this gives all of your lightsaber attacks +2 damage, it essentially takes the place of four points of strength for lightsaber specialists. (And really, how many guardians are going to be using long swords?)