Where do you find a competent editor? I put the question that way because I believe every serious writer hires an editor to go over the manuscript before sending it to a publisher or an agent.
Paying that person can easily make the difference between a sale and a rejection. Once you sell the manuscript, you still go through the editing process explained in the previous postings. No matter how well you write or how well you've been edited, another editor will find things that can be made better.
Think of the money you pay as investing in your writing career.
So where do you find a good editor?
Try to get a referral. Ask other writers or agents at conferences. Go online and type in freelance editors, but be careful that you get someone who has experience (and you'll want to read their résumé). A group called Freelance Editors has been around for several years and so has the Independent Editors Group. I know of two groups that edit Christian books: The Christian Communicator Manuscript Critique Service, owned by Susan Osborn, and Kathy Ide's Christian PEN: Proofreaders and Editors Network. There are many others. (I've used the same woman for years and I'll be delighted to send you her contact information, if you request it.)