the Vancouver group started out small..4-8 people, but now it's huge..20-30 people. :)
What they do is, everyone brings their extra coupons to share, (lots!); and people start plunking down envelopes, file folders, shoeboxes, etc., etc., on the tables, and everyone takes a turn looking through everyone else's 'coupon stash', and pulling the coupons they want from it. :) (only bring your 'giveaway' coupons!)
The unofficial 'rule' is 'be fair'; if there's 20 copies of a coupon you want, (and of course, now there's close to 20 people there), only take one or 2, and check again later to see if you can get a few more.......that way everyone has a chance to get some great coupons!
As well, as people start to know each other, and their 'coupon wants/needs' :), they'll start to bring specific coupons to give to specific people, ie. if you need lots of Pamper coupons, and I have tons; I'll bring them for you. :)
If you take a peek on the Calgary coupon forum, (go to Local, then Alberta, then Calgary :) ); you'll see they chat back & forth quite a bit, to find out in advance who is looking for specific coupons,.........as people who have large coupon 'stashes' won't necessarily drag out everything, if they don't know what others specifically are looking for. ;)
hope this helps. :)