A good fight scene (and a good smut scene for that matter) always works in the service of the narrative. It works toward the cohesive big picture.
From an entertainment standpoint, violence is boring.
You need your audience invested in the characters participating in the violence, in the actions and events leading up to the fight, in the aftermath and how this will effect the character’s overall goals.
In a narrative context, if you’re bored during a fight scene or a sex scene it’s because the build up to that moment failed. The scene itself may also have failed. However, your foundation is what makes your story sing.
Think of a story like building blocks. You’re playing Jenga with your reader on a homemade house, they’re slowly pulling out the pieces and you’re betting you built your blocks well enough to withstand scrutiny. You’ve got to keep them interested long enough to get to the end before the whole thing comes tumbling down.
A fight sequence which works in concert with it’s narrative is enjoyable, doesn’t overstay it’s welcome, and ultimately works to build up the story it’s telling. Fighting isn’t fighting, you see. Combat is a form of problem solving, the fight itself is an expression of the character’s individuality. Everything we’ve been learning about them, their goals, and their behaviors are being put in a pressure cooker and dialed up.
You should be learning about the character as the fight progresses, the fight working on multiple levels in concert with its narrative to get the story where it needs to go. Often, a first fight is like an establishing shot in film. You get a feel for who this character is when under pressure, who they are. Peril can be a great way to get the audience invested, but its up to the author to prove why they should.
Poor fight sequences don’t tell you anything. They’re there to establish the character as capable of fighting but don’t even do that because their concept of combat is generic.
The combatants aren’t individuals expressing themselves, the fight isn’t proving anything except fighting, it doesn’t have meaning except for its attempts to prove the narrative’s poor concept of badassery. This often happens with no regard for the setting’s rules, the aftermath consequences, what the character’s actions will effect in the long run.
It doesn’t mean anything and, while violence is shocking and terrifying in real life, in fiction violence has to mean more than just an exchange of blows.
How many times have you read a book where several mooks show up to get their ass kicked by the protagonist? They limp off at the end and while they’re often in a perfect position to be seen again due to their connections, we never do.
In even just a moderately competent narrative, those same mooks are characters. We’ll see them again in bit roles. They’ll play a role, either to help or hurt later as an aftermath consequence of the protagonist’s earlier actions. These are callback characters we can use to remind the audience of what happened previously in the narrative, and offer up some catharsis.
In a really well written scene, these mooks serve an important purpose when it comes to establishing the protagonist’s character in a quick snapshot. Like the moderately competent character, they come back later to the aid or the detriment of the protagonist. The mooks’ response actions are a direct result of their encounter with the character, often acting as an inciting incident. The protagonist suffers direct consequences as a result of their actions, whether its injury, loss, or the attention of the villain which causes them to lose something. In these fight scenes, you can see the story’s trajectory because it acts as another way to get to know the hero, the secondary characters, the tertiary characters, and whoever else is participating. It’s working on five different levels.
What you often see in a good fight sequence, whether it’s in a written medium or film, is the culmination of a great deal of hard work on the part of the author. A smut sequence is a reward, it’s a way to pay off on the reader’s investment in the relationship between these two characters and the narrative’s investment in them. It doesn’t matter if that’s hardcore sex, or a Victorian hand touch, or a knockout blow to the jaw, the end result is the same. It’s entertaining, satisfying, and even cathartic.
A poor sex scene is just dolls bumping bits. A poor fight scene is just dolls trading blows. Nothing occurs, nothing happens, there’s none of the underlying satisfaction or catharsis in the outcome. You don’t have any investment, no consequences, it overstays its welcome and tells you nothing about the characters.
You’ve no reason to care, so you don’t.
As a reader, you don’t owe a writer attention when reading their work. They’ve got to earn it. If they aren’t, then it may be that the story isn’t for you and that’s okay. Take into account your tastes,
It takes practice to choreograph a fun fight scene. Writing sex and violence is mostly about learning to find your limits (i.e. what you’re comfortable with writing), and overcoming embarrassment. Determine the difference between need and want.
Are you avoiding writing these scenes because you’re scared of being bad at them or because they just don’t interest you?
These are two very different issues, and it’s easy to hide from the first behind the second. Be honest with yourself. If it is fear, then don’t give into it. The easy solution if you’re afraid of being bad at something is to practice. Start looking critically at the media you consume, when you start to get bored during a fight scene or a sex scene, when you want to skip ahead, ask yourself, “why?”. Check out the sequences and stories where this doesn’t happen, and try to figure out the differences between the two.
When it comes to the mechanics of both violence and sex, the more you learn the better off you’ll be at writing it. The more you practice writing violence/sex/romance then the better you’ll be. Like with everything, it’ll probably be pretty terrible in the beginning but the more you practice, the better you get. Writing itself is a skill, but its also a lot of sub-skills built in underneath the surface. Being good at dialogue doesn’t mean you’ll be good at action, having a knack for great characterization doesn’t mean you’ll be good at writing setting description. Putting together great characters doesn’t mean you’ll automatically be good at worldbuilding.
Don’t be too hard on yourself.
All it takes to figure out whether or not the time to fight is right is by listening to your gut.
Remember, the best scenes are based in narrative cohesion and emotional investment. They’re a pay off in and of themselves for your audience, dessert after dinner. They aren’t the meat and potatoes. If you set out to just write a fight scene or write a smut scene then it’ll get gratuitous. Then the focus is on the fight or the sex itself, hangs entirely on their shoulders, and you’ve just upped the ante for how entertaining you need to be.
It’s not “how do I write a fight scene”, it’s “how did my characters get to this point and why are they fighting”. If you start from a character place, it gets easier. The same is true with romance. “How do my characters participate in a romance (sex or not)”.
Make it about the individuals, that’s when it really gets fun.
And, if you get too stuck, try writing fight scenes with characters who don’t know much about how to fight. Sometimes, it’s easier to get into it when you begin at the beginning. There’s a lot less pressure convincing an audience with a character who knows nothing than one at the top of their field.
There’s a lot less stress about “is this right?” when you’re trying to get a feel for the flow if you’re dealing with a character who doesn’t know jack shit. Fight scenes with characters who know nothing can also be really, really, really fun. They’re wild, improvisational frenzies where all you have is the character sorting through their alternative, non-fighting skills trying to figure out how to survive.
Believe it or not, this will help you because you don’t get to cheat with the idea that your character already knows what they’re doing when you don’t. It’ll help you tap into the character, seeing scenarios from their perspectives, and writing to that instead of “generic fight scene”. When you’re unsure, characters who know nothing about the subject matter they’re engaging in but still have to engage are great. They teach you how to write from the standpoint and perspective of the individual. You need those skills just as much when writing characters who are professionals or at the top of their field.
If you don’t think you can write an interesting fight sequence with a neophyte, then that might be a part of the problem. A character doesn’t need to be good at something to be entertaining. A smut sequence where everyone’s fumbling, knocking into each other, embarrassed, stuck in their clothing, cheesy, corny, and laughing can be just as fun (if not more so and more honest) than the ones that generally get envisioned.
For me, good is entertaining and the entertainment is based in humanity but you need to define “good” for yourself in your own writing. Be honest with yourself about your fears and you’ll find a way to bridge yourself to the kind of writing you want to be doing.
Freeing yourself of your own internalized preconceived notions will help a lot, and produce stories that are way more fun.