My 25 Birthday

Hi
I need ideas for a scavenger hunt that I want to do for my birthday this Sunday in the West Los Angeles area. My friends are all between the ages of 21-28. We are all pretty crazy and want to have a fun and rsiky scavenger hunt. Please tell me how I go about planning this and what a scavenger hunt requires as well as any ideas to do in the LA area. I would appreciate your help. Thank You