How do I film a friend's wedding? My friend asked me to video tape his wedding. I have minimal experience behind a video camera but I'm comfortable with technology. I'm mostly looking for composition and logistical advice on filming a wedding. 

I think my friend's expectations are low but if I'm going to do this I want it to be at least worthwhile. Thus I have read that besides keeping the couple in the viewfinder the next most important aspect to shooting a wedding is to have a mic on the groom for the ceremony. I don't have a wireless mic but I figured I would put an iPhone in his pocket with the headphone mic pinned under his lapel and sync the audio in post. Is there anything else I'm missing?
I have never filmed a wedding, but here are some tips on shooting video in general.
1. Get a good tripod. This is critical if you are doing panning shots. I use a 3-way fluid pan head.
2. Don't zoom or pan too fast. If you feel like you are panning too slow, that is about the right speed. Even though it feels really slow, it won't be when you are watching it later. When zooming, make sure your zoom are even and steady (no bursts of zooming). I usually set the camera's zoom speed so that it is not variable. Don't zoom in, then immediately zoom out to correct the zooming in, unless you have two camera angles.
3. Get two (three if you can) HD cameras if you can. HD makes post much more flexible as you can make minor in/out changes. Two cameras makes also makes post "easier". If you are only using one camera and you accidentally bump it, it's hard to correct. Two-three angles make filming much more reliable.
4. Use 16-bit audio on the camera(s) that you are recording from. The default setting is usually 12-bit, which can slowly drift out of sync towards the end of the video.
5. Film in 16:9.

I hope this helps you out.