Do you have fight scenes in your book? What does your character used to defend him or herself; a gun, a sword or even his bare hands? How much do you know about how to use a weapon or use your hands as a weapon?
My protag is a muscle bound assassin who is feared in his world but when he has to come to ours he is on unlevel ground. He's suppose to come here, find his prey and leave without being known but he gets found out by a young woman who will be his partner throughout the rest of the story.
The young woman, Kristina is the key to the story. She has abilities she is only just learning about, but she also has fighting skills. Her parents sent her to self defense classes blah, blah, blah. How do I convey that in my writings?
I have some knowledge of martial arts. Not much. I am a brown belt. Like I said, not much, and I didn't want Kristina's fight scenes to look orchestrated, so what did I do? I studied hand to hand combat and martial art videos and read articles from well known people in the martial arts arena. I even watched myself in a mirror with a weapon to see how to make it look real.
My assassin's skills and even the marine in my novel had to feel real and I hope that I have accomplished that with what I have learned, and there is magic in my book also.
Alas! that is another story. Study your characters abilities. Try to make them as real as possible. Research is the key, so don't treat it like poison ivy.