Give it one last read-through. Look for the right words in the wrong places (e. g. a typo which turned out to be a correctly spelled word, so spellchecker missed it). Look for sense and ease of understanding. Make sure your plot makes sense.
By working with a three-tiered scene and character system, both you and the writer can focus better. If Betty the Barista is important, then the story really needs to focus on her dark eyes, her jaunty beret, and the rose tattoo on her left shoulder. If she's just seen in passing, then she probably doesn't even need to have a name.
The best way to get an editor is to do some research. Ask people you know are published. After all, an editor no longer has to live in the same city or country as you (but you will do best with someone who is a native speaker of the language your book is in). Work with the editor on a sample chapter. Do you get along? Are his or her suggestions reasonable? Are they slow?