People say I'm pretty good with action scenes in my books. I've won second place in a action catogory in a contest once on the first draft of one of my books. lol I usually can picture things in my head pretty good like a movie, for fighting scenes I just put in music and go. Mostly Bad Reputation by Joan Jet because it's got a good action kind of beat to it.
I tend to think I am pretty good at it, actually. Sometimes I go so far as to think it has or is becoming one of my strengths as a writer. Particularly with fights. What helped me?
Learning to fight.
I think that all the time I've spent, in my life, studying martial arts has done a lot for helping me write fight scenes. It gives me theoretical knowledge and practical experience to apply. Also, studying how others write action scenes is helpful. That should be obvious. I'm less good at guns and cars because I don't drive and have never shot a gun. If I wanted to get better at them, I'd go learn. I think experience is one of the best steps you could take to improve.
I don't think I'm that good with them, at least not in making them elaborate. That's why most of the time the action I write is very short and basic. I don't go describing in amazing details how awesome the fight is or how the characters make some hard to believe martial arts moves and back flips and what have you. Things just end up short and bloody and in your face without much decorations. I suppose that sort of style has its appeal in the world of fantasy seeing as the genre is usually peppered with elaborate fights.
I'm no R.A. Salvatore who can have three chapters in a row with nothing but action. And he makes it work.