Susan Gable said:
Yeyeman, invest in the book Self-Editing for Ficiton Writers by Renni Browne and Dave King. Read it carefully, absorb the craft stuff, and use it as your guide to do your own editing.
From Self-Editing Fiction for Writers by Renni Browne and Dave King (which I agree is a great book):
"True, you can hire an independent editor to work on your manuscript. In fact, there is no better way to get the editing you need--though our opinion may be biased. But even if you do hire a pro, you want your manuscript to be as strong as it can be before you have it worked on. After all, why pay for editing you can do yourself?" (pages 2-3)
i.e. never send your first draft to an editor. Not only might they refuse you (or charge you an arm and a leg), but you do indeed want to do as much editing yourself. However, it never hurts to have a qualified set of eyes help you do the final polish when you can't see anything more wrong with your work.
They also warn that critique groups may result in you writing the book the critiquers want, not what you want, and that writers don't always make good editors. Something to keep in mind as you go through the critiquing process.