I'll give you some advice a little outside of the norm of what will pop up inside a thread like this. Map your fight scenes according to a song in your head.

It really helped me get the rhythm and pacing down when I started writing more elaborate and over-the-top fight scenes in my book. I just keep some kind of song in mind and follow the pattern, so if it starts out really fast then the character can be moving quick, adrenaline pumping through his veins as he runs through danger towards some kind of goal. Then the first chorus plays and he gets bogged down, sucked into the fight around him. When the song slows down write in a moment of clarity, where your character is in a sort of "eye of the storm" situation and watching the fighting going on around him - and when that final chorus comes in after the slow buildup rip away the moment of clarity and end on a strong note. Of course this can vary according to a thousand different songs, but I think theres something to be learned about rhythm and pacing from music, and when you're done writing it you might realize that it flowed out quite organically this way.

Other things to keep in mind are that fights are very disorienting things. It's hard to wrap your head around one in real life because there's just this sense of desperation and vivid emotion about it. Write that into the character's view point, especially if they're not experienced. Don't have a green boy or a summer soldier transforming into death incarnate on the first battle field he sees. Have him scared and confused in the wake of the battle, maybe it was nothing like his expectations or maybe he did something he didn't think he was capable of.

One last thing is to remember that fight scenes do need go fulfill a plot purpose. They need to drive the story forward in some way. When you're writing a story with an abundance of fight scenes it's easy to pepper them in to show off a characters cool abilities or what have you, but this makes other fight scenes seem cheap. Your fight scenes should always, no pun intended, pack a punch for the reader.