The Companies office has a good list of stuff we need to do before incorporation. Simply put, we need - some Rules (a constitution): I've found a Sample Constitution we could adopt - a signature onthe above by a Justice of the Peace - 15 or more members who all agree that incorporation is a Good Thing - a rubber stamp (yep! I laugyhed too): its called a Common Seal.
Also check out the SCA website. I have no idea what they are but they seem to be doing something similar to us with the Society of Creative Anachronism: http://www.else.net.nz/inc/index.html