Simply becoming a member of the site doesn't guarantee a place to stay...so here are some helpful guides to get started in the CS community and culture.
http://www.couchsurfing.com/mission.html
http://wiki.couchsurfing.com/en/Searching_and_requesting_a_c...
http://wiki.couchsurfing.com/en/How_to_write_a_CouchRequest
http://wiki.couchsurfing.com/en/Cheat_Sheet
(I'm heavily involved on CS)