First, it helps to have friends that spar and to have sparred a little on your own. I have been lucky that I have spent a decent amount of time around martial arts experts and former military and have sparred myself so I know the logical flow of moves. Failing that knowledge I would say that you, as a writer, need to decide what type of fighting knowledge your character has. Are they a street brawler? A martial arts expert? A weapons expert? How do they handle themselves. Once you figure that out, watch movies or TV shows that feature those types of fighters on Netflix, DVD or any format where you can pause and play back,or look up scenes on youtube. Then play the scenes over and over and transcribe it. Which way do the characters shift? How do they move their feet? Their arms? Describe the movement of the weapons? Then get up and move the way the characters are. Get a feel for the movement, get it into your mind. Once you have done that, you should be able to visualize it in your head enough to describe it. What makes fight scenes a challenge is writing them in an order that makes sense. I had to rewrite a rather complicated sparring scene (three characters, multiple weapons) about three times before I was happy with it.
I am very proud of and picky with my fight scenes and it's paid off. One thing I am repeatedly complimented on from martial artists, former special forces and others, is that my fight scenes are like watching a movie. In Honor Bound, the character Cesco is the main fighter. John and his sister Clara are close behind in skills but Cesco moves faster than normal and has heightened senses and as such is point man. In writing him I had to portray his competence, how his mind works and how his movements flow because his fighting skills and movement are such an integral part of who he is. I have several training weapons and I was literally doing the movements in slow motion in my living room as I wrote the scenes.
I think fight scenes can be overlooked in writing by a lot of people but if you have physical combat just stating “He punched him in the stomach, then kicked him,” almost seems trite. It's my belief that realistically describing a combat situation, even if it is a quick one, can bring quite a lot to a story and show another level of the character that may not have been evident before. How fast do they react? What are they perceiving when they fight? How you answer those questions can tell a reader much more about a character than a chapter of character development can.
I hope this little post makes you think both as a writer and a reader and that if you get the Honor Bound Series you will enjoy them. Please leave reviews when you finish reading!