How do I film a friend's wedding?
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.