1st Rule: You do talk about Bar Camp.
2nd Rule: You do blog about Bar Camp.
3rd Rule: If you want to present, you must write your topic and name in a presentation slot.
4th Rule: Only three word intros.
5th Rule: As many presentations at a time as facilities allow for.
6th Rule: No pre-scheduled presentations, no tourists.
7th Rule: Presentations will go on as long as they have to or until they run into another presentation slot.
8th Rule: If this is your first time at BarCamp, you HAVE to present. (Ok, you don’t really HAVE to, but try to find someone to present with, or at least ask questions and be an interactive participant).

I’d also offer folks the opportunity to document the event or particular sessions on the wiki as an additional form of participation — since not all participation must be verbal.