John Scalzi, a very talented humour writer and novelist (I like to think of him as the "edgy Dave Barry"), has written a bunch of notes for the newly married gays and lesbians of Massachusetts:
It's your best man's (or the equivalent's) job to remind people that at a wedding reception, as at the Academy Awards, speeches are best very short. You didn't spend an obscene amount on the catering just to have it grow cold as Uncle Jim blathers on.
Remind the DJ or band that they work for you, and they'll damn well play anything you want. For some reason I think this may be less of a problem at gay weddings. Thank God.
There will be drama of some sort at the reception. If the wedding party lets any of it reach the newlyweds, they haven't done their job.
Don't fill up on bread. You'll have to dance later.