Title self explanitory, what do I get? What should I avoid? What should I do? What should not get into the habit of doing? etc etc etc

Ok, first you need to think of a few things.
1. Music - use music YOU like. Ofcourse it's got to work, but if you don't like it then you're gonna get super bored half way through and not finish it. Happened to me plenty of times. Look for hard hits and good "sync points".
2. Recording - Fraps is generally used, I think. If you can, record in full screen and use Bezcam (unless you feel like doing freecam). Multiple angles tend to make a video step up a level.
3. Vegas - it's the go to program with this, windows media player isn't really good enough. With Vegas if you want tips and such, people on the IRC can help, but a better source would probably be YouTube tutorials, they're very useful.

Obviously there's a lot more than that, but you know, that's the basics imo

The most common mistake I see nowadays is that people sometimes put the replays to the music and they won't even speed them up to match the pace of the music. It really glazes my donuts when people play speedcore to a replay recorded at 15 FPS. I always speed up my clips to make them as fast as the music.