I try to clean it up as best I can. But my editor still finds thousands of errors.
I search for telling words (end in ly etc.). 'When, could see, to, are also good one to look for. Filter words like felt, saw, heard, etc., since I usually write single POV. Freeloader words (that, very, quite...) I have a huge list I search for. Its not that they are bad, but they may help to pinpoint other issues, and an editor won't necessarily look for these things. They're just polishing my turd of a MS
In addition I'll look for words I tend to repeat, and attempt to clean up dialogue and descriptions. My editor fixes all my tense issues. I'm horrible at it. I'm also horrible at general grammar rules and my editor will have to rearrange a sentence here and there.
It's best not to get too carried away. These aren't mandatory rules someone should follow. If the sentence sounds ok to my ears, I won't change it. I can get so carried away that the sentence will not sound any better after all my effort, and will probably violate some rule or another.
I'll catch plot inconsistencies on the multiple read-through's. I edit immediately after finishing the draft. I like the story to be fresh.
But the more I correct the easier it is for my editor to find other things. And the more I write the easier it is for me to catch these things on the fly.