If you are on the road to writing your first book, or second, or whatever, here’s a tip I totally believe in. When you’re done (or as done as you think you ever will be), go through it, run the spellchecker, run the grammar checker if you have one, then leave it alone for a day, or a week. If you can, print the whole thing out as a hard copy. And then, when you are feeling a little bit distanced from your work, sit down and read it through as if you were a reader, not the author.
See if you connect with the characters. Read the dialogue OUT LOUD and see if it sounds natural or contrived. Listen to your instincts; does something not feel right. Is something, a situation or event feel a bit…off? That’s the reader in you telling you that something is wrong. Listen to that little voice! Re-read that section until you figure out the problem. Don’t assume it’s fine or you’re just imagining things; you probably aren’t.
There is no such thing as too much editing. Try not to obsess of course, but make your creation as good as it can be. The reward will be happy readers, and after all, isn’t that who we’re writing for?