Scrapbooking exchange on our cruise.

[I_love_Cruising]

I'm trying to set up scrapbooking exchange for our cruise book, because several people showed interest in participating.
I have never participated in a scrapbooking exchange before, so I'm a bit lost on how to go about it.

What would be good rules to start with?
Is it usually a finished page that is exchanged or just some elements and everybody creates their own page or adds it to their book.

I would love to hear about your experiences with cruise scrapbooking exchanges. The good, the ugly and everything in between.