This page does not go into full details of the combat system. It does not address critical hits or crit builds.
For a more in-depth read, see StrategyWiki's article on combat.
Any reference to "attack" or "to hit" are the same thing.
Bonuses to attack are more valuable than bonus damage because missed attacks cause 0 damage.
The final boss has 38 defense without buffs. A character with +27 to hit will hit 50% of the time. A character with +36 to hit will hit 95% of the time.
There is always a 5% chance to hit or miss, regardless of stats. A character with +0 to hit will hit the final boss 5% of the time.
Thus, +36 is a good benchmark to aim for. This guide's guardian build aims for +40 to account for -4 from flurry.
Always invest in the two-weapon fighting feats as soon as possible when dual wielding/double blading.
The two-weapon fighting and dueling feats never work together.
If a character is already invested in two-weapon fighting (Carth, Bastila), continue investing in it rather than moving away.
Conversely, if a character is already invested in the dueling feat (Mission, Jolee), do not invest in two-weapon fighting.
If dual wielding, always use a "balanced" weapon in the off hand. Double-bladed weapons and blaster pistols are always balanced.
Double-bladed lightsabers are best for damage and use fewer lightsaber crystals.
The best lightsaber build for melee-focused builds is Heart of the Guardian with Upari and Phond crystals.
For non-jedi melee (Canderous, Zaalbar), use two fully-upgraded Baragwin Assault Blades (purchased on Yavin). You can purchase the first after completing one planet after Dantooine, then purchase a second after completing all five planets plus Taris.
Two-weapon fighting does not affect two-handed ranged weapons such as blaster rifles.
You gain +10 to hit against things that are very close.
Melee attackers get a bonus against targets with a ranged weapon in-hand.
This guide offers very little advice on ranged combat. My preferred build for ranged companions is dual wielding pistols with rapid shot, using the second Sith Assassin Pistol and a fully-upgraded Cassus Fett's Heavy Pistol. The second Sith Assassin Pistol is acquired during the main quest when you reach your final planet, and Cassus Fett's Heavy Pistol can be purchased soon after that once you are automatically approached by a special merchant.
It is not possible to raise defense high enough to be meaningful against the final boss. There are better ways to mitigate damage anyway.
Saves are made in response to a hostile effect, such as stuns and force powers.
Most effects that require a save are nullified by Immunity: Mind-Affecting and the Force Resistance power.
The save stats can be safely ignored.