I think it's always scary to start, but asking us is actually showing humility and total fear. That's good. 
Well, you know how many of us who shoot weddings do it, if you've read the "doing my first wedding" thread.
1. Have back up equipment always. If you already have good gear, that's great, but there is nothing worse than a camera failing at the wedding and you don't have backup. So, get yourself another camera if you need to, borrow one, rent one, whatever, but 2 is always better than one.
2. Yes, it's all about the bride. But if I were doing this for the first time, I'd look at some of the threads here to get group poses (Jeff-Toogy), Tim, Lloyd (Picturecrazy), Kathy H and Leesa are here in this forum a lot and have great shots. If you can ignore the silliness, the Albany Wedding meet had some great ideas. You'll learn a lot from the 17 of us that got together.
3. Meet with the clients to see what exactly is expected, poses, how many shots, when you will be getting them to the client, etc. The business part is at least 1/2 of what we do.
4. Wear black, be as stealthy as possible. Professional and in control.
5. Do several views, take pictures from different heights, angles, distances. Don't be afraid to zoom in right off. Some photographers shoot far away and hope to crop later, but I find I need to compose the shot seeing all the distractions and dealing with them as I shoot. That takes time and practice. I don't like th PP something out later.
6. If you have any questions about lighting and such, ask now.
And good luck! Tell us what gear you are already planning to take with you.