Oh boy. This is a big one. Sigh ...
Finding an editor was one of my biggest challenges. It made the cover design look like a cakewalk (and it truly isn't, it's stressful, and very important to find the right designer!)
Lesson 1: Just because someone says they're an editor doesn't mean they have the qualifications to edit.
It's hard when you walk into the indie world because everyone and their mother is an editor it seems like, and yet you can't find one! A lot of avid readers that have been able to spot errors in books get the epiphany that editing is their calling. I am not saying anything negative about this group. Some of them I'm sure would make great editors. However, it is really important as a writer that you know what you're looking for when you're seeking an editor.
Things to consider:
1- Do you want just line editing?
2- Do you want content editing?
3- How many rounds will your editor go (I learned after asking this question to someone I was interviewing, that you need to be specific here! I am not asking how many times will they read through the story for corrections before returning it; I'm asking how many times will your editor go back and forth with you. If they send you corrections and suggestions, are they going to review them? How many times? At what cost?
4- How do they charge? I personally prefer to use editors that go by word count, not time.
5- What Style Guide do they use?
6- Do they have a contract? If they don't have a contract, I would honestly say to keep shopping. You need to have something to refer back to for time frames, expectations, etc.
7- Will they do a sample edit for you? This is another thing I feel is mandatory. You need to get a feel for what your potential editor is going to be able to do for your story. Read their comments and suggestions and take them into consideration. Is it what you want?
8- Have a phone conversation! You don't need to become besties with your editor but you DO need to be able to communicate, get along, and make sure they understand the message of your story so that while they're editing, they can be making sure it's clear.
9- Get multiple quotes. The first few people I met I thought, "She's perfect! I found my editor! This was so easy!" A week later I was singing a completely different tune. When you're new to the writing world, you don't know what to look for. You see some corrections and suggestions and suddenly the person is not only qualified but brilliant. Compare sample edits, see what each person offers.
10- READ SOMETHING THEY'VE EDITED!!! I read two books from each editor I was considering and it did make me pass on several. There are always going to be mistakes, they're inevitable, but how big are they, and how many of them are there?
11- What's their editing experience? Did they go to school for it? Are they a fellow writer? Avid reader? Etc.
12- Do they have a proofreader? I really think everyone should have a proofread in addition to an editor. It's another set of eyes to catch small mistakes.
13- Do they charge you for their time? I met a few people that allotted a set amount of time to discuss the marks they sent you, and if you had additional questions or concerns they charged you by the hour. This IS a job for them as well, you have to be realistic, but you also need to ask yourself if you want that kind of relationship with your editor.
Lesson 2: Don't be afraid to ask more questions!
If you're feeling inferior, or concerned from your interactions with a prospective editor, ask more questions and if it doesn't change, move on!
Lesson 3: The best place to find a good and reputable editor is by looking at the acknowledgments of your favorite books.