Any videos by Jerry Ghionis or Cliff Mautner would be helpful. I've learned a lot from them. I know Jerry has at least a couple of classes on B&H's YouTube channel. KelbyOne has a bunch of wedding tutorials from Cliff, but it's a pay site (excellent learning experience though).
I'm only on wedding #5, so take that into consideration, but I've learned a few important lessons so far. (In no particular order)
1) Wear comfortable shoes. You're going to be on your feet a lot.
2) Get a schedule from the Bride/Planner so you know where to be at what time. That'll help you make a shot list. Google it and you'll find a lot of them.
3) Get there early, or research the venue online, to get an idea what you're in for (lighting, size of the space, shooting locations, etc.) Attend/shoot the rehearsal, if possible. I've shot in a theatre that was huge and on a yacht that was pretty tight, and this research has been very helpful for me. Then I get my game plan together and choose what gear I'll need based on the situation. Once I'm more seasoned I'm sure I'll have to prep a bit less, but I like having a good idea of the environment I'm getting myself into at this point.
4) I LOVE my BlackRapid Double Strap. It lets me carry two bodies securely all day, as comfortably as I can imagine they could be carried. For those times when you only need one camera, it snaps apart quickly to make a single strap.
5) Do your best and have fun. I've been amazed at how many family members have thanked me, hugged me, brought me water bottles, etc. and they haven't seen a single image. That's a nice feeling.