There are basically two types of player when it comes to combat: The Tactician and The Thespian. The names are fairly self-explanatory, but they deserve a bit of detail.
The Tactician is the one who carefully plots out every permutation and sequence of the combat, carefully managing her character’s skills, powers, and resources to maximize her impact on the combat. Don’t be surprised if she uses a ruler to compute line of sight and cover. The Thespian will just say, “I leap off the balcony, swing over on the chandelier, and drop on the ogre’s head.” Don’t be surprised if he doesn’t even know what die to roll.
The key to managing combat is engaging both types of player (and other players in the spectrum, because yes, it’s a spectrum) and keep it moving.
The sweet spot is giving the Tactician enough crunch and the Thespian enough dramatics. Exactly how much is beyond the scope of this work, because it’s dependent on so many variables, every player is different, and every table has its own dynamic. You’ll have to recognize it, and you will, because when you hit the sweet spot, it’s immediately obvious. The awesome part is that, if you use Rule 3 properly, both will take something cool away from the combat. The Thespian might say, “Oh, that’s cool, I didn’t know you get a bonus if you’re in front of him and I’m behind him.” The Tactician loves it when you verbally describe how his clever use of rules and strategy splatters the foe across the room. Both end up in inside-joke stories they’ll tell for years.
Either way, you need to be descriptive. Which leads us to…
Part 2 – If you’re going to be descriptive, take the time to be good at it.
Nothing is more boring to both the Tactician and the Thespian than describing combat like this:
“Okay, uh, the monster does 5 points to you, Annie. Jerry, you’re up.”
Foes are more than bags of hit points that do n damage per x strike or y ability. I mean, yeah, n x and y are all important, mechanically, because the target may be resistant to piercing damage or something, but taken by themselves they don’t make for good story.
Be aware of what the foe’s abilities are, be aware of what they do. It’s all right there in the monster description, so use it.
Let’s use Drow Elf as an example, taken right out of the SRD.
Shortsword. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage.
Hand Crossbow. Ranged Weapon Attack: +4 to hit, range 30/120 ft., one target. Hit: 5 (1d6 + 2) piercing damage, and the target must succeed on a DC 13 Constitution saving throw or be poisoned for 1 hour. If the saving throw fails by 5 or more, the target is also unconscious while poisoned in this way. The target wakes up if it takes damage or if another creature takes an action to shake it awake.
All the mechanics are there. The monster can do 5 points of damage to Annie’s character. But that’s so lame, so boring. All you have to do is describe how the 5 points are done. It’s easy.
“Annie, Einreb sees the female Drow whirl toward him. She smiles evilly as she raises her hand. You see a tiny glint of metal before you hear the snap of her hand crossbow firing. The small bolt zips toward you. You try to dodge but it finds a gap in your armour, and you feel a sharp pain which begins to spread like fire throughout your body. Take 5 points of piercing damage and make a Constitution save, please.”
All of that is based on the hand crossbow information in the monster description. It’s nothing difficult or out of the ordinary. But it’s exciting, isn’t it? At least more exciting than “5 points. Next.”
 When everyone starts talking about “…how much fun that session was, oh, wow,” STOP. Don’t let anyone leave. Ask them what made it awesome. Make a note of that. That’s how you repeat that. By the same token, if a session ends poorly, ask why and note that, so you can find a way to mitigate or avoid it.