If there're two things to remember about wedding photography, it's that you have to know your stuff inside and out and second chances don't exist. This helpful video will show you some great tips for posing a large wedding group, lighting them, and picking the proper camera settings.
Coming to you from Shutterbug Magazine, this video contains advice from the one and only Denis Reggie on properly posing, lighting, and shooting a group at a wedding. As a wedding photographer, you'll no doubt have to do this with lots of groups during the formal portraits, and it can be a taunting task if you don't head into it with a plan of attack. Luckily, as Reggie demonstrates, you don't need super crazy equipment to get good results; in fact, he's just using his Canon Speedlites, a radio trigger, and a white umbrella. Speedlites are probably preferable for most photographers at weddings anyway (unless they have a dedicated assistant hauling all that stuff around), as the speed and convenience makes it much easier to jump around and keep up with the fast pace of the day. Don't forget if you're a Canon shooter that there's also the Yongnuo version if you're looking to save more.