My personal preference is to have lots of dramatic lulls in the combat, and some minor character introductions or development if you can manage it. If you can find a way to create mini-characters out of nameless redshirts, that also seems to be entertaining.
I feel like what precedes the combat, and the peripheral events that happen during the combat, may be more important than the combat itself. Describing the action is necessary to an extent, but if it's constant description of movements your combat will get boring quickly. Where do you draw the line between technical action, dialogue, and description of emotion and other things not directly related to the fight itself?
It's a balance I'm still trying to find. I think my weakness is a tendency for too much exposition, but I do try to add elements that tell a miniature story as well. A couple years ago I felt like I was getting close in a storygame I predictably never finished. This is what I had written then in a rough draft (if this helps you, great; if you find something that needs improvement, by all means please comment, but the point is to show what I think is one decently done thing and one poorly done thing, which I will specify at the end):
Things were not going well. [insert stuff about how intelligence was wrong and the lines have been breached and repaired numerous times throughout the day]
During the last twenty minutes, a lull in the combat nearby had allowed you to catch your breath, and despite your instincts protesting against it, you rested on your knees, using your sword and shield to support you.
A shrill voice from behind you draws you back to attentiveness and you stand. A boy runs up to you, carrying a skin of water and parcel of some sort. "Captain, General Mathers sends word that the 43rd Division will be unable to aid the Northeastern flank." The boy, hands on his knees, takes a deep breath and continues. "They were attacked from behind by an auxiliary force of mercenaries, and while disposing of them another hostile unit from the north arrived, this one bringing more than men."
Troubled by this new development, you watch as the boy takes a drink from the skin and then hands it to you, his breath still coming out in ragged pants. He can't be older than 1o or 11. Sparing a quick glance to your left to make sure the line is holding steadily, you ask, "What do you mean by 'more than men,' son?" Turning back to the melee, you take a deep drink and await the answer. In the distance some twenty more enemy soldiers approach.
"Ogres, Captain," says the child. "General Mathers says at least ten accompany another squadron of enemy soldiers, and that they'll have to make their retreat this evening. They were nearly routed when I first ran, Captain. He begs you consider sending the running reinforcements here to the East to help along the Ilowaen Forest, and begin your retreat one night early to meet him at the next defensive position."
You feel frustration bordering on panic at that. Ogres? Rumors were already circulating among the commanders nearest your position about reanimated dead soldiers attacking on some portions of the Eastern perimeter, and what little you knew of the overall defense plan and intelligence suggested a powerful magic user may be behind the attack. But ogres? Twelve feet tall and nearly half as wide, alone they were terrible foes. If the enemy has somehow convinced them to join them in numbers against the Kingdom, things are far dire than you had previously believed.
A flurry of shouts and metallic clangs to your left signal another breach along the line. Resignedly you raise your sword and shield. "Boy, what's your name?" you ask, eyes never leaving the fighting just ahead. One of your men gets run through with a spear, and then two enemy soldiers spot you and begin to approach at a fast walk.
From behind you the boy says, "Oliver, if it please you, sir." Not taking your eyes off the two approaching men, you loosen your shield buckle and let it slide down.
"Grab the shield, Oliver, and run back twenty paces. Keep the shield up in case that one throws his spear at you. If I fall, strap it to your back and run as fast as you can to my second in command, Lieutenant Marks, and inform him that he has command. Deliver him the message from General Mathers and then retreat to the next position." You look back and see the boy frozen, staring at the shield. "Oliver!" you yell. "Do you hear me, boy?"
Shaken back to awareness, the boy nods. "Then go, Oliver, now!" He picks up the shield and begins to run back. Knowing the boy is temporarily safe, you turn in time to see the two soldiers reach just outside of your attack range, their pace more deliberate now.
The two fan out as they approach, flanking either side of you, and in the distance you see a third approaching. The one on your left holds a spear, the other two short swords and shields. The flanking soldiers exchange glances, and then the one to your right screams and charges. Anticipating the charge is really a feint to draw your attention away from the spear wielder, you immediately turn to your left, swinging your sword down. As you expected, the other man planned to stab you from behind, and your sword deflects his spear to the ground.
Stomping hard on the blade, you pin it to the ground with your foot and sword, simultaneously drawing your dagger from your belt with your left hand. In a single, swift motion, you fling the blade underhanded at the spear wielding man, and the dagger strikes him directly in his unprotected face. You turn back just in time to deflect the sword strike from the other man with your own sword, and then kick his shield to gain distance. As he stumbles, you turn back to the other man and finish him with a stroke to the neck from your sword.
Pulling out your dagger just in time, you use it to parry an overhead swing, pushing it to your right, then you step around the man and stab your sword into his right side, just underneath his armpit. You quickly slash him in the throat with your dagger and he falls, hot blood soaking your forearm.
You pivot to face the final enemy, but before you can react, a savage strike lands on your unprotected upper left arm, exactly where a hole in your mail armor had been made earlier in the day. The pain is shocking, but you manage to hold on to your dagger. The enemy steps back, and the two of you square off.
He slowly swings his sword in an arcing figure-eight, and then leaps forward, attacking you on your left side, trying to gain an advantage from your wound. Knowing your left arm may be too damaged to go where you want it to, you jump back and parry with your sword instead, taking the defensive. You try to raise your left arm back up to use the dagger as a fighter would with a rapier, to parry attacks and thrust with your sword, but the pain nearly makes you feint. You let your left arm hang low, but hold onto the dagger so your opponent is forced to assume it is still a viable threat.
The man attacks again, and you are again forced to step back. Suddenly your foot lands upon one the men you just killed and you slip to the floor. The man comes in for the kill, but a blow from behind causes him to turn back: the boy named Oliver struck him with the shield. Wasting no time, you quickly leap to your knees and lunge at the man's groin with your sword. In defense he swings down at you, but you are able to raise your dagger arm high enough to take the blow with the flat of the blade, holding it reversed so your forearm supports it. You drive the sword in deeper, and the man's own sword falls from his hands. Standing, your sword still deep with him, you cut his throat with your dagger.
As the man falls to the ground, you look at Oliver. "I would chastise you for not following orders, Oliver, but you saved my life. Thank you." The boy, still in shock, doesn't seem to hear you. His chest heaves rapidly, and he sways before you. You slip your dagger back in your belt and place your hand on the boy's shoulder. Kneeling, you say, "Oliver, look at me. You're okay. You're a hero, son, and I need you to carry my message." The boy seems to perk up at that and meets your eyes. You hold his gaze for a moment, then you squeeze his shoulder and stand.
...
Now, what I like about this excerp is the little side character Oliver gets a tiny bit of interaction with the player, and manages to go through his own mini-story arc. It's a little bit god-from-the-machine, but I feel like it adds some additional depth to the battle situation. I feel that too often, combat scenarios, especially battle sequences, forget about the peripheral things that go on, like messengers running from position to position to deliver intelligence when other means fail. I feel like here, that was done pretty well.
What I don't like is I feel I'm a bit too descriptive with the combat. I think I can streamline it, maybe a lot. Some of it I think is necessary and adds some character (like the main character having an injured left arm, but refusing to drop the dagger so that the enemy must respect it as a threat), but some of it was way overboard in move-by-move description.
So, the point of this example was to show what I believe is one thing done passingly and one thing done poorly in combat description. DO add some things not directly related to combat, some stuff on the periphery; DO NOT spend an excessive amount of words saying which sword goes where and how long which swing lasts. Give enough information to paint a reasonably clear picture, but save the detailed description only for the key moments.