You’re going to have to figure out whether it’s standing grappling or on the ground. If it starts standing, it’s going to end on the ground. Grappling can be very dynamic, if you understand the basic thought process.
1) It’s all happening in a very tight space.
Grappling means you’ve moved past the point of punches and kicks (aka you are too close for them to work) unless we’re talking about some very specific kinds of techniques designed for work in a space with limited arm movement such as the uppercut or a knee.
At this distance, the general point is to destabilize your opponent so you can put them on the ground. (Preferably without going with them, but if you must be the one on top.) This means a fair amount of shoving, seizing of the arms, grabbing the neck, chokeholds, etc, but sequences where the two fighters are essentially just dragging each other about in an effort to get the other to lose their balance. This can mean knocking each other into walls, tables, chairs, or just maneuvering their feet.
The general assumption with grappling is that it’s all about upper body strength. It’s actually not, where you put your feet and your ability to maintain your balance so that you stay standing is far more important. You’re close enough to smell what the other person ate for breakfast, there is no room for full extension of the arms. You’re going to go round, and round.
2) We all fall down
This will not last long, however, because someone is going down and it’s going to be hard. Write them falling over.
3) Someone is going to land on top.
Ground fighting is a scramble. The one who goes down first and lands on the bottom, the one who goes down second and ends up on top has the advantage. It’s also a question of gravity and weight, weight matters a lot more on the ground than it does while standing.
180-280 pounds bearing down on your chest is a lot, 120-170 is also a lot.A 90 pound woman can hold a significant advantage over someone while sitting on them. People are heavy, if you’re on the bottom that’s essentially you trying to lift that or shake it off. Without decent training, most people don’t know how. Most people don’t know how to make their arms and legs work together on the ground, long before we get into even basic grappling techniques.
If you land on your stomach and they’re on your back then it’s over. Their weight will bear down on you, they can pin you to the ground, grab your head, slam it into the pavement, choke you out, and you can’t do a goddamn thing to stop it. You can’t really get up and crawl away, no matter how strong you are. It is, however, the first instinct to flip over onto your stomach as opposed to staying on your back. This is one of the places where natural instinct will screw you over.
Being on top can be the difference between victory and defeat, especially depending on whether the one of the bottom managed to trap them between their legs or they escaped to jump onto the stomach. If your character knows how to lock up an opponent in the guard, then fine. If you have no experience with holding someone in “the guard” (aka you wrap your legs around their waist to keep them away from you), then don’t bother really. It’s more likely whoever got on top has managed to bypass this stage.
From the position sitting on the stomach, it’s the perfect position to start wailing on the other guy. They can just hit them a metric ton or move to try to strangle them. The punches may not be that effective, but they’re going to hurt a lot. You can expect at least a broken nose if any land on the face.
One basic way to defeat this is to buck, the bottom person widens their legs, braces their feet, and jerks their hips straight up much like a reversed bucking bronco in an attempt to unseat the other person. The success of the technique will depend on how well the other person can keep their balance (and the bottom’s skill at keeping it up under pressure). Done right, the top’s body is going to come forward, the bottom grabs one or both of their arms, twists their hips, and rolls sideways into their opponent’s guard thus reversing position.
More realistically though, someone’s just going to end the grappling bout with their face getting pounded into the concrete.
That’s all assuming no one breaks anything on the way down and no one hits or lands on their head. If one goes down and the other doesn’t, then they’re just going to start kicking and stomping them.
Never go to the ground unless you have to. You’ll still end up there.
You don’t have to say everything, you do have to paint a clear picture of what is happening. Move swiftly from one action to the next, keep a sense of kinetic motion going, play up the tension, make sure you know what position is a good one and what is a bad one, and manipulate your characters into them.