Plan out your fight scenes. Stage them if necessary. (Humm. I think it was in another panel where someone talked about using Lego figures.)
And consult with people who know.
Also, if the character is experienced, he's not going to think about the step, pivot, etc. -- he's just going to think, hip throw.
There's levels of realism, and it's important to know whether you're dealing with James Bond or someone who actually gets hurt.
And some discussion about how most people aren't accustomed to fighting and will probably pull their punches and the like. You can get away with not killing the man hit five times with a tire iron if you put it in the hands of a man who doesn't know how to do it right.