Reading out loud is a great help at this stage, checking that it reads smoothly. The big proviso is that you must read accurately - I notice that quite a few students read what they'd like to see rather than what is actually on the page. Words get cut, contractions are made etc which simply aren't there. These are some of the things I look for:
* cliches (heavy heart, golden curls)
* autonomous body parts (her lips curved into a smile)
* active description
* strong verbs
* strong nouns rather than adjective plus weak noun ( a breeze rather than a light wind)
* check dialogue attributions
* be direct rather than passive
* use specific words
* name names and be consistent
* watch out for similar character names (I write as someone who once had Pat and Patrick in the same novel
* delete qualifiers - a little, very, just, kind of, sort of, quite, rather
* watch for repetition
* check grammar, spelling and punctuation
* vary paragraph and sentence length
* vary starting words (it's all too easy having a whole para filled with sentences beginning the same word)
* avoid unnecessary punctuation eg exclamation marks and italics, capital letters, underlining.
I could go on, but instead I'm going to recommend two books: The Elements of Style by Strunk and White, and Self-Editing for Fiction Writers by Browne and King. They're both really helpful when editing.
If you're really lucky you have a nit-picky friend who'll happily edit your work. A friend like this will sometimes make you say 'thank you' through gritted teeth, but remember that you don't have to change anything and it stops you having to do as much work. Edit, edit, and edit some more until it feels like your eyes are going to fall out and go splat on the manuscript. But it will be worth it and soon you'll be on to the last stage.