I helped out with a videoing a friends wedding a few years ago and the best advise I can give is as follows:
1) Take more film than you think you could ever use because we you edit you can cut film but not add anymore than you already have.
2) Make sure you have spare batteries for the camera and a charger, ideally you want 1battery in use, 1 battery spare and 1 battery charging.
3) Take as much footage as you can. The more the better.
4) Use a tripod, seriously it make all the difference between crappy amature photography and good photography.
5) Take and use some basic lighting because the night crack whore look isn't a good look for people.
6) Use a mic.
7) Don't do tricky zooms, a nice transion or pan is much better than trying to capture all the action. (no Wayne's World zooms, it's not good).
8) Remember good composition (1/3 from the top/bottom and 1/3 from the sides) makes anything look good, and don't try to get too much action in the one frame, not good.
9) Make sure before the wedding you ask the bride, groom and family what they want you to video, get a shot list because you can't build a house without a plan.
10) Single brides maids are easy to score off and if you do don't tape it, each hole is a goal
