This is a bit of a guideline to give you some idea on Bonus XP earnings. Keep in mind that these are exactly that—a guideline, and the base guideline that I use. The actual earnings are nearly ALWAYS adjusted for the specific circumstance, such as if someone endeavors to bring snacks that are more than a mere bag of chips, or if they have a character higher level than the average character.
Snacks for the game: 250 XP
Giving the DM/other players a ride: 100-300 XP
Assisting other players with leveling up/character creation: 250 XP
Providing a gaming place: 500 XP
Creating content on the wiki (once edited or approved by me):200+ XP