What sort of fighting is it? Is it organised fighting (if so what kind; boxing? martial arts [and there are heaps of martial arts]?) Street fighting? An action movie with fighting scenes? A 'kung fu' homage?
And it depends on what you want to do with your fight scene. I actually rehearsed my first fight scene yesterday. Turned out one of my actors has her stunt license and the other is a tae kwon do instructor, so they taught me way more than I did them. Personally, I don't like violence, so we worked out a way avoid glorifying the violence - the fighting is hard to watch and very realistic (and quite different to regular movie fighting).
But I recommend talking to 1) a stunt co-ordinator and 2) someone with a lot of fighting experience. If you want to make it "cool" they'll know ways to do that. If you want to make it realistic, they can talk through ways to do that, and how people respond in real fight situations. Etc etc.
I would work out some very rough choreography, then talk to a DP about the best way to complement that choreography, depending on what you want to achieve.
Of course, also analyse a hell of a lot of good fight scenes and see what they do well (hint: if the sound is off, you ruin the whole experience and make it laughable - I saw a good fight scene recently, but they used the same two punching sound effects and it completely distracted from the piece).
Sorry that's not a very direct answer.
