I try to give out bonus XP to account for good roleplaying, particularly interesting in-character actions, or just something funny that happens. It's part of my typical XP speech which goes like this:
"Everybody gets X thousand experience for killing monsters. Everybody gets X thousand experience for stopping the demonic invasion of Baphomet's fiendish minotaur warband (or whatever other goal the PC's are working to accomplish.)
Kent, you get X experience for bravely spitting in the eye of Gur-al-Tumar, Warmaster of the Minotaurs, when he offered to let you surrender.
James, you get X experience for solving the Riddle of Baphomet and figuring out how to close the Gate of Nightmares.
Leo, you get X experience for working in the most Mr. Gumby quotes during the adventure."
Seems to go over well with my folks.