Additional XP Rewards

The two major player pacifiers are XP and treasure (usually in that order). XP is only officially given for killing monsters. If that's the only reason why you ever give XP, you'll have nothing but a bunch of hack-n-slayers on your hands. Psychology 101: Behavior that is rewarded is encouraged. Here's some suggestions for behavior that you might want to encourage.

(Note: the XP bonuses are merely suggested figures. It's up to the DM to adjust these based on what he wants to see more of or less of.)

Action XP bonus
A witty quip that makes everyone at the table laugh 1-4
Good roleplaying 5-25
Good roleplaying even if it endangers you or means some kind of loss 10-50
Playing your alignment 5-15
Not playing your alignment (may warrant suggesting an alignment change, if possible) -5 to -15
Clever solution to a problem 10+
Helping your teammates 10+
Helping your teammates even if it means some personal risk or loss to yourself (giving up a wish, going back into the swack-iron dragon's lair, etc.) 30-100 or more
Voluntarily giving up some treasure to another player 30+
Voluntarily giving up some treasure to another player for whom it was obviously intended50+
Being an excellent team player, providing great support 5-10
Cooperating with the DM 10-20 or more
Telling other players that it's their turn in the initiative round so that the DM doesn't have to always do it 1 per incident
Assisting the DM in some way (looking up a rule, spell, etc.) 1-5
Completion of a major mission objective 100+