I give out XP based on the following categories. :
1. Combat
2. Skills (especially class skills), natural talent (ability score checks), and other non-magical abilities
3. Magic, psionics, and other supernatural powers
4. Roleplay (character interaction, behaving in character)
5. Adherence to values of your group (religion, order, race, culture, etc.)
6. Style (cool moves, creative use of skills, powers, the environment, etc.)
Each character is eligible for a certain amount of XP per session, but the amount is divided differently among the ategories based on character class, race and background.
I also give out a little bit of bonus XP for the following:
1. Attendance
2. Metagame (enhancing everyone's fun, keeping things moving, etc.)
3. Progress made towards character goals (must have goals to be eligible)
4. Progress made towards party and mission goals
Until recently, I used the 3.0 method but I switched because I found that it made the game too combat oriented because my players feel like they were wasting time when they weren't in battle gaining XP.