*Writing Fight Scenes for Fun and Non-Profit*
I've noticed that, similar to lemon scenes, some authors have problems (or think they do) with writing action scenes. It never fails. Ask on any message board what kind of writing gives authors the most trouble and you'll see, more than any other answer, lemons and fights. The two aren't necessarily separate, but we'll go ahead and treat them as such, at least until we hit the fights-leading-to-sex scenes. There is a real difference between a fight scene resulting in death and a fight scene resulting in two fighters making love in their ring. Now obviously your scenes will depend on your story and your characters, but there are some universals that we can consider.
*Kicking Ass And Taking Names*
This is it, the scene itself. Don't freak out, it's not that hard. No matter what type of fight you're writing, be it a gun battle, vamps vs. werewolves, kung-fu or sci-fi laser action, the same basic rule of thumb applies.
You don't have to describe every punch, kick and shot. If you do, your fic is gonna come across as amateurish, and might even make your reader laugh without meaning to. I'm talking about fight scenes to go like, "he hit him with a right, a left, another right, grabbed the bottle and smashed him over the head." Hmm, not too bad, but it comes off a little like a bad detective novel. If you tried to novelize the Dragonball Z series, you wouldn't describe every single punch traded. You'd be stuck on the Saiyan saga for a thousand pages, never mind Frieza.
You only have to describe what counts. Par down the hits and instead go for the characters' reactions to them. Ryoga picks Ranma up and hurls him into a table. Describe the wood smashing under Ranma and how the hit knocks the breath out of him. He goes through and lands on the floor. Does his head hit the floor? Does he lay stunned a moment? Does he grab a bottle and fling it? Does he have to roll to the side to avoid Ryoga's umbrella?
Vegeta kicks Goku into the side of the cliff. Does the rock crumble? Does Goku brush the dirt off his gi and attack? Does he cry out as Vegeta kicks him again before he can move? Vegeta doubles over from a series of punches to his abdomen. What does the pain feel like? Bring back any painful memories?
Don't assume this means your fight scenes have to be short. They can be the whole fic long. They can be ten or twenty pages. They can be novel-length. As long as they're interesting. Keep the tension high, keep the comedy high, keep the character interaction high, keep the drama high...seeing a pattern here? Also, you can drag the fight out as long as you maintain a balance between the punching and the character thoughts. Too much of one and the fight is flat. Too much of the other and it's barely a fight anymore.
Dialogue and inner landscape will be your best friend. They help flesh out your scenes and give you room to write beyond the punches being landed. The mind doesn't shut off automatically in a fight (sometimes it might, but not everyone's does.) They may get tunnel vision, things might appear too clearly, their heartbeat pounds in your ears, their breathing comes faster. There is an exhilaration, an excitement, in the moments leading up to a fight. Blows might not hurt as much initially. They'll start to feel them later. The bruises will start almost instantly. Depending on who's fighting, there'll be regret or delight, pulled punches or lethal swings.
You'll also want to have a groundwork understanding of how the character reacts to pain and what damage can do to a body. Unlike the movies, people who are shot do not get back up, I don't care if they were just grazed. Now if your character has been shot a few times before, there'll be some resistance to the shock and they can keep fighting, but a first time bullet is one hell of a shock. Different caliber bullets can either sting or knock you on your ass for the whole fight. Same for a knife. If it's a fight for their life, they might be able to handle it, but there has to be some serious adrenaline to ignore stab wounds. Ki blasts burn, and burns sting like a bitch when you pull them. People bleed quickly, from headwounds moreso, and could faint from loss of blood.
*Using Confined and Open Space*
One of the first things to consider when is the environment in which your characters are fighting. This isn't just about a barfight including broken bottles and slamming into the jukebox, it's about the type of fighting you'll be writing. There's a difference between a fight in a confined space, like a room or a field, and in an open space, like a whole city or shopping mall. I realize the mall may seem confined and the field open, and they can be if treated as such. However, a field, no matter how large, is still just a lot of grass. Even if you add a river, some bushes or a tree, it's still a field and your characters won't interact with much but eachother. From the writer's standpoint, they may as well be in a closed, empty room.
Confined and open spaces both have their advantages and weakpoints, and both can be drawn out or suppressed as need be. For example, in a confined space, you limit the area your characters can move in. This heightens tension and suspense, as well as places the spotlight on your characters. Ever seen Black Magic M-66? Part of that anime takes place in an elevator with an android trying to kill the two humans inside. On a pure plot level, the audience is at the edge of their seat wondering if the humans will die.
Confined space can also help you bring up the tension that will help drive you to your fight scene. Consider two rivals who hate each other. Put them in a small room, seated on opposite ends of a table, facing each other. They stare, the tension gets higher, and one of them snaps and attacks the other. Obviously this will vary considering your characters, whether it's Spike and Vicious, Tamahome and Nakago, or Ranma and Ryoga.
For open spaces, you offer yourself more opportunities for both comedy and violence. There are more things to interact with and plenty of room to write. Let's look at the given examples of a city and mall. A fight scene in a city either involes a lot of cars and helicopters or very powerful humans/aliens. They'll be zipping across the skyline, leaping off of rooftops, crashing through billboards and neon signs, hitting the street and destroying cars, flinging portable toilets at eachother, crashing through theaters...don't make the mistake that Power Ranger episodes and Godzilla movies do. Buildings aren't empty. They are full of people, water lines, electric wires, gas lines, people's embarrassing personal items...use all of your dramatic elements and remember that if a building is destroyed, at the very least there's a large amount of dust, panic, office paper and people breathing in their dead vaporized friends.
The shopping mall, conversely, is most likely for mostly regular humans, and ups the ante on character intereaction as well. The mall could also qualify as a confined space, but strap a pair of roller skates on one of your characters, give the other Buffyish vampire qualities, and suddenly you have a fight that'll go from Dillards to the Disney store, up the escalator, through the bathrooms and out the Mexican restaurant, with all the taco flinging and mall cop assaults that'll follow. Chases through the shoe shop, hiding in the fitting rooms and maybe, if your fight takes place in a wholesale warehouse, a fight in the rafters.
Of course, there are drawbacks to each space. If you opt for the tiny room, you'll have to rely on character to get you through. This isn't bad unless you're only rehashing everything they've said before and you aren't that great at blow by blow accounts. If you go for the big mall showdown, you've got a lot to work with and you might be overwhelmed. Or you could rush through it and skim too much on the details, and it'll seem thin.
Now don't freak out about having to write one type of scene in one type of space. Remember, you're a writer. Even if you write yourself into a corner where you have to use one space where you think the other would've been better, you can draw out the positives of that space and make it okay again.
This type of combat is ideal for characters with no combat experience or characters too weak to fight. In a verbal fight, punches are still being thrown, but it's being done with words instead of fists, and those words can devastate in a way normal fisticuffs can't. Your words can hit below the belt and earn an instant knockout, or slowly whittle a character down until they can't stand up, both on the levels of plot and character building.
Ultimately your characters will dictate what they say, whether they are warriors flinging insults before combat, a wife confronting her husband, two lovers sparring in the bedroom, a group of philosophers arguing theory. The main thing to remember in a verbal match is your pacing. Yelling, screaming and throwing things can fit in very well with a slow, steady rise in tension. You can use small jabs, like one character baiting another, the wronged wife's leading questions or charged comments, and build up to a dramatic right hook, her coming right out and confronting him. A prime example of this is Firecracker's story Chichi's Torment, in the first confrontation between Chichi and Goku. She baits him, calls him names, gets nasty, and then lets everyone in the room know that he was boinking Vegeta.
Alternatingly, you can go for a surprise spinkick that no one was expecting, a bombshell comment where you then must deal with the fallout rather than the buildup. A team suddenly discovering a teammate's betrayal, just imagine their reactions. Shock, disbelief, rage, sadness, all could come out, at least in part, whether or not you follow it up with a physical fight. In fact, a fight might lose you some of the tension already built, though you could of course write your dialogue in between real punches. Fight or not, this type of verbage would probably tend towards lower, muted speech, whispers or quiet voices from one person. Going back to Chichi's Torment, while his sons and wife are still loud, Goku is suddenly quieter.
*Or Fighting and Sex*
Ultimately, while a fight is character tension that must be resolved in combat, it comes down to character tension, and that tension can be resolved with violence, sex, or both. While the nasty solution of rape falls herein, I'm talking more about how violent tension can be turned into romantic and/or sexual tension. This explains to everyone who's ever asked how we can pair characters who are portrayed as disliking or hating each other, or who exist as rivals, like Kaiba and Yugi, Wufei and Treize, Count D and Leon Orcott, Bulma and Vegeta.
Hate and love are two sides of the came coin, and one can easily turn into the other. Strong feelings are still there, but the attitude only has to change slightly to fit our needs. And it can change in midfight. Most of us, especially in the DBZ realm, have read at least one story where the two rivals are fighting and end up in bed. This works for you Bulma/Vegeta het fans as well as the Vegeta/Goku fans. After all, sex doesn't have to be about love and love doesn't have to be the sappy kind. I've said it before, there's all kinds of love, jealous love, possessive love, romantic love, psychotic love, violent love, and you've got to understand exactly what kind of love your characters are into. Just because you want your pair to be sappy doesn't mean that's what the characters want.
This goes back to how you're writing your characters. Vegeta can be written as romantic, shy, vicious, cruel, demanding and submissive, all successfully. But if you slash him with Goku and have them punching the shit out of each other for half the fic, both of them angry and at least one of them out for blood, Vegeta won't suddenly turn around and become the weepy uke. Likewise if he's the weepy uke, don't expect your reader to believe it if he turns into a superconfident seme. Now granted, if you want to write him like that, go for it. You might be able to pull it off. But you're gonna have to make it believable.
And believability is the most important part of this love between rivals. For these kinds of pairings, especially the Wufei/Treize pair, there are a lot of naysayers who don't think they could have any kind of relationship, slashers and het alike. Usually the means to "get them together" is provided in the canon. Wufei admires strength, and Treize is one of the strongest characters in the series.
When writing fights between rivals, you might add a few double entendres. The more confident fighter would probably say them, baiting his rival and keeping him off balance with his comments. Weaknesses would be verbally manipulated, the weaker rival would probably be teased and mocked. And remember, at the end of the scene, whoever won the fight didn't necessarily win the subtextual battle. Say Wufei manages to disarm Treize and has his blade to the taller man's throat. With a smile and the right verbal jab, Treize can still stun Wufei. If it was a Hollywood movie, the heroine would have the gun on the villain, but her hand would be trembling and the villain would come slowly closer, talking all the while, until he gently pushes her hand aside and wins.
On the other hand, if Treize wins and has the sword on Wufei, the possibilities for sexual conquest are myriad. There's enough subtext between the two to elevate them from rape to love, especially since Treize is such a charmer. If one character seduces the other, though the uke may have regrets and doubts, he would probably continue to return to his seme's arms. In this, the battle has gone from the physical to the subtextual again. The fight hasn't stopped, only transformed.
*Writing the Damn Thing*
At the end of the day, you're the writer. You write your own rules. As long as you make your scenes work, then fuck the rules and keep going. You don't have to research this in real life, but when watching a movie or reading a book, pay attention to the fights and think about what makes them work. Conversely, think about what might be keeping them from being good fights. Finally, if you need a book-long example of fight scenes, try the book Armor. It's a scifi, it's rough and sick in some parts, but damned if it won't teach by example how to write great fights.