hmm... try reading other works? or instead of describing the visuals, try to describe the abstract but real pain the character is feeling

Depends on the kind of fight. Whether it's between thugs randomly punching each other or experienced martial arts masters.

In the latter case, it's kinda difficult if you haven't studied martial arts yourself >_<

Matt Stover, one of my favourite authors, prefers to concentrate on describing the emotions, aura & energy of the fight.

He's been criticised for it by some but I actually love that method of narrating fight scenes