Here's a link I found invaluable. If you look under the "Video Techniques" section you'll find excellent articles that are really top notch IMO. I'm no pro and have a lot less video experience than most here, but for starters I found these to be excellent, especially the ones on focusing and white balancing. I think they are just right for those starting out (not too much and not too little) but the principles are basic and usually hold long afterwards:
http://www.backscatter.com/learn/article/
There are lots of opinions and you'll probably see other answers from the experts here, too.
Those "Jump settings for blue water video" from that link will create a total nightmare for a beginner. And gain does not always need to be at 0dB. You'll want some gain in darker situations and it won't get noisy (grainy) until it's over about 9dB.
Start with white balance set to manual and learn how to do it using a white slate, a white fin, the sun, or just the palm of your hand (which is what I now usually do). White balance very regularly as you change depth.
Switch everything else to auto and see how it goes. Keep the lens and port absolutely spotless and you might get away with auto focus 99% of the time, especially in good viz.
When you're happy with the basic handling, white balancing, framing etc. then if you want you can try manual focus next and later manual iris and shutter speed. Manual focus for wide stuff is a case of focussing on the reef or your fin or something and then locking it and leaving it. But for macro stuff you'll want to manually adjust it shot to shot if you're in auto mode. I still use auto a lot for wide stuff unless I'm shooting something like a manta or whale shark in dodgy viz and I fear focus "hunting". But I think the majority on the forum opt for manual more than I do.
Above all think steadiness steadiness steadiness. This is the biggest thing that differentiates accomplished underwater video work. And don't pan around too much. Let the subject do the moving. Think of each shot almost like a photographic still.