You may become proficient in various fighting styles as described below by spending weapon proficiency points. You can put a maximum of 2-3 points in a style for increased benefits.

Fighting Style Eligible Classes
One-Handed Weapon All
Weapon and Shield Warriors, Priests
Two-Handed Weapon Warriors, Priests, Mages
Two Weapon Warriors, Rogues
Fighting Style Description
One-handed Weapon Characters who specialize in this style gain a special AC bonus of +1 while fighting with a one-handed weapon and no shield or off-hand weapon. By spending an additional proficiency slot, the character can increase his AC bonus to +2, but that’s the maximum benefit for style specialization. This style increases the chance of a critical hit.

Two-handed Weapon While wielding a two-handed weapon, the specialist does additional damage and the weapon's speed is lowered, making it faster. This is the only style that applies to two-handed weapons.

Two Weapon This style involves using a weapon in each hand to attack. This provides additional offensive power and the second weapon could be used to block incoming blows. Obviously, a dual-wielding character loses the ability to use a shield. Any one-handed melee weapon can be used in either hand and they can be of the same type. Thrown and missile weapons are not permitted choices when dual-wielding. If not trained with this proficiency, the character suffers a –2 penalty to attacks with the primary weapon, and a –4 to attacks with the secondary weapon. This penalty is offset by the character’s reaction adjustment for high Dexterity. Generally, your off-hand only ever gets one attack. Rangers automatically know two-weapon style.

Weapon and Shield A character with this skill will get an AC bonus vs. missile attacks. It applies whenever a shield is held. These bonuses may be combined with those for One-Weapon style.