Something every blog post I've read on this subject has taught me is to "REST" my work... When you've written everything and you're fed up of the sight of it, put it away and leave it alone. It might be for a few days or maybe even a month - just make sure you leave it alone so that next time you look at it, you'll see it with fresh eyes. Stephen King used to put his finished drafts in a draw for at least six weeks... have a little patience with your art.
Read Your Book
It might sound a tad obvious but read it, but don't just read it in your head, read it out loud. Hearing where you stumble over sentences or find yourself short of breath will help you to see where your readers are going to get lost because it's over wordy or perhaps contains bad grammar. I recently learned your computer can tots read it for you too, if you are feeling a bit lazy.
We all have words and phrases that we accidentally cling to and use again and again. They are guaranteed to bore our readers and so they've got to be deleted. Most of your work might escape the dreaded delete button but don't let these words get through. Remove or Replace, it doesn't matter just make sure your readers don't ever find out what your overused words are, they should totally be a secret between yourself and your book drafts.
You might think you are cheating but spell check is actually a life saver so use it. Don't ignore the squiggles and lines - they do mean something! At the very least make sure you know why spell check is disagreeing with you.