Don't make it easy! Everyone loves a good fight. You don't the winner to win without being challenged. Make it close and let the other guy get a punch or two in. It makes it much more realistic as well. A guy who is obviously going to loose is going to walk away from a fight. If they're an even pair it makes the fight more likely.
Don't forget the consequences! Another thing I never really considered but now think it is huge. After a fight, you fall off the adrenaline high. You are achey or injured or something. Maybe the winner is excited and energetic. Make sure to explain this part as well! This part makes it more realistic and segues into the next scene of the book.
Don't overdo it! Give the readers a break. Back to back to back to back action scenes is going to get old and the reader is going to loose interest. Reading all action doesn't let the reader take a breath. Action scenes can take over a story and the plot becomes irrelevant. If the main character is constantly running, hitting or fighting they becomes unrelatable.
Humor! This is always a nice way to make characters fun and witty. Don't make it too gritty and raw, add in some funny moments or funny banter. Characters talking smack is fun character development. If they're about to fight or if they're doing an action, don't forget that they're still characters. They talk, they feel. Add in humor and you're making a scene that much better.
READ READ READ! Read books that have action in them. Become familiar with them so you can subconsciously understand. Pick a book in a similar genre and take note of the action scenes. Don't mimic them but get a feel for it. You'll pick up common themes and words.