Here's my tips:
be familiar with the types of weapons involved in combat. Not an expert, just be aware that a short sword is more of a stabbing weapon, a longsword a slashing weapon. This will help in your descriptions (and for most swords, thrusts, jabs, slashes and hacks will be good enough verbs).
get a list of all the kinds of verbs to describe an attack. A thesaurus may help. For martial arts, know all the kinds of real attacks most schools teach is useful. One my blog posts has such a list (as I posted one of the monk schools I wrote up, based on my own background). You don't need to be an expert, but just having a sense of how these weapons are used will help you describe attacks beyond "you hit him for 8 damage"
When a player makes an attack, describe each attack differently, using your newly upgrade vocabulary.
Don't overly describe the damage. Firstly, it gets cumbersome when the GM tries to get gruesome. Nextly, since damage in D&D is nebulous, you don't want to commit to a specific injury, lest the players try to lobby for special effects based on that injury. Additionally, combat is fast paced. Your descriptions should be as well, to invoke that feeling.
Since combat takes place in 2 5'x5' squares, there's plenty of room for side-stepping and moving and jumping, enough to explain a miss, besides just blocking it with a shield, or parrying with a weapon, be bouncing off his armor (which are also good explanations).
Here's some examples of what I tell players during their attacks:
"you jab at him, but he just barely sidesteps"
"he catches a grazing blow from your hammer"
"he deflects your attack with his sword, and readies to return the favor"
"your blade skips across his armor"
In all cases, keep it short, and choppy, just like combat itself.
Never use a description that adds more actual event or action that what happened mechanically. If your hammer attack can't knock somebody out of their current square, than don't describe it as "your hammer blow sends him flying across the room." Additionally, since you'll be describing how a PC avoids getting hit, you don't want to ascribe an action the PC didn't actually take, nor block him from his next action that he can legitimately make.