It really depends. There's a lot of mood, character and situation going on that influences. Generally there is a lot of "alright, so..." and waving my arms around trying to re-create the action though.
A lot of it is based off of what my players do, if they "Swing," then they "hit". If they "Come in with an overhand chop", they're "parried at the last moment."
"Alright, so you hack into that goblin, then swing at the next, but don't connect." or "You slap him around." is usually what I do for mooks. A few verbs or adjectives are all it needs.
The rest, well it just sort of flows. When an assassin drops a smoke bomb and jumps off of a balcony, holding the edge to cling to the underside only to be followed by the ninja-in-a-dress, who dives into a kick, the descriptions tend to write themselves.
If you can get a little give and take going, even simple "he does..." followed by "I do...." really builds into a good beat. And I've found that hitting the beats and bringing some play into the game is much more beneficial than flowery descriptions.