Write, re-write. Read and re-write it again. How often to writers hear that advice? But here's one problem. Since the writer knows what the entire novel's supposed to say, he/she can't always see some of the shortcomings. One way to get around this is don't look at the book, listen to it. There are a number of text-to-speech programs a writer can use.
I've used a free downloadable version of Ultra Hal (from Zabaware). Yes, it sounds like a B or C rated superhero, but it's actually been helpful in finding things that just didn't sound right when I'm not looking at the screen. It's definitely a useful tool for self-editing.
Good luck and Write On.