I really enjoy writing a good fight, or chase. Action scenes can be difficult though, because there's a lot to balance. You have to make sure that the reader gets enough information to clearly follow what's happening, without slipping out of POV, and without giving so much information that the tension collapses under the weight of it.
The first hurdle is moving the reader from "no action" to "action" in a way that doesn't confuse or jar them. For instance, a made up on the spot example:
Garin crouched to examine the floor, running his fingers over the weathered wood. The dust had been disturbed, but not too recently. There was already another thinner layer overlaying the footprints. His world narrowed down to those prints, and what he could ascertain from then.
He barely noticed the squeak of the floorboards behind him, and by the time the sound's meaning penetrated, it was too late. He started to jerk upright when a heavy arm slipped around his throat, pulling him up and back against an equally heavy chest. The forearm crushed against his trachea just enough to limit the amount of air he could pull into his suddenly frantic lungs.
In this example, Garin registers the squeak of the floorboards, so we know that someone is coming up on him, but he's so intent on what he's doing that he doesn't at first realize what it means. If he hadn't registered them at all, I couldn't tell the reader about them. And while I have no doubt this all comes as a surprise to Garin, I think it's important to telegraph your punches for the reader. Too abrupt a switch, even in a scene where some sort of action might be expected, can feel jarring. For instance...
Garin's mind focused on the prints, on their width and length. A man, then, or a woman with large feet. Not an elf, and certainly not a gnome, although perhaps a--
A heavy arm wrapped around his throat from behind, pulling him up and back against an equally heavy chest.
Even with the dash to indicate the interruption of Garin's thought, this feels disjointed. There's no smooth transition and the reader has to process what is happening, while they're reading the sentence in which it's happening. Because they don't know what the end of the sentence is when they start reading it, it's difficult to parse the action. Sentences aren't absorbed as a whole until they've been read. So, here we have Garin thinking about the foot print, and then suddenly there's an arm. If you don't know what's coming next, the way a reader doesn't, it can be confusing.
The details of the telegraphing can also provide vital information. In the first example, the squeak that provides the telegraphing is behind Garin, which tells the reader about the positioning of the attacker in relation to Garin. Since we know that Garin is crouching to examine the floor, an image forms. The attacker is walking up behind Garin, and Garin is crouched. The reader has an understanding of the logistics involved.
Taking those logistics into account is another important step in constructing an action scene. I think the key to any action scene is a clear picture of what's happening. Seeing the movements of the characters lets you ask questions about how they would react. And when imagination fails, there's always getting up and trying it out. Obviously, the more complex moves are going to take more imagination--unless you're a stuntman or a martial artist, etc.--so it's important to cultivate the ability to visualize these scenes. It's a skill, like any other, and the more you practice, the more details you'll be able to add to the scene inside your head. That translates to more details on the page.
For instance, because we know that Garin is crouched, the attacker has to bend to reach in around him. The arm then pulls back as the attacker straightens, pulling Garin up and backward. If Garin is crouched, his weight is probably pushed forward, onto the balls of his feet. So, when he's pulled up he is off balance for however long it takes for him, specifically, to adjust. I then look at the character. Let's say that Garin is a trained fighter. Adjusting his balance would be reflex, even (perhaps especially) in the face of a surprise attack.
However, say Garin isn't trained at all, hasn't even ever been in a street brawl. Maybe he adjusts just to remain standing, but maybe he also panics. What if he overbalances? He could send both himself and his attacker sprawling just because he's off balance when he's pulled to his feet. Especially if he's taller than the person who's grabbed him. Does that person know how to adjust for that? Are they trained?
Knowing your characters is as important here as anywhere else, but you can't ask yourself the important character questions until you know what's happening in the scene.
How do you plan out your actions scenes? How much of them come out in the first draft and how much do you have to rewrite or rethink later?