After spending a fairly good portion of my weekend life doing weddings professionally, (30 to 40 a year), I can advise you that getting a contract signed & agreed upon price. That all the rest will fall in place. Times are different now. Digital imaging has allowed everyone to be fairly good. Your professional attitude, posing, and control of the event will show your customer and everyone else that you are the true professional photog.
when I started it was with a 4X5 speed graphic for BXW, a Rollei for color, 2 strobes, a tripod and extra stand. That alone made me the Pro. As a guest, respect the Pro and his expertise. I think in most cases he will appreciate it and cooperate. Good Luck :thumbup: