I was recently asked, “How much editing should a writer do themselves?” It’s always hard to answer any question with a “should” in it, because the answer is different for everyone. We also need to know what the goal is? To send the work to an agent? Or to self-publish?

I’ll describe what I do when writing novels.

1. I write my first draft. For each book I’ve written (I’m wrapping up my third), my first draft has become much better. 
2. Then I make a first editing pass on screen. I’m looking for a bunch of different things, including:
1. obvious typos and grammer mistakes
2. places where I did too much telling and not enough showing (one of my chronic issues)
3. obvious continuity errors: I changed a characters name, or their occupation, or where some characters were, etc.
3. Individual chapters are shared with my critique group after my first pass. On average, my critique group sees about a third of my chapters for any given book. I fix any issues the critique group identifies, which can be about clarity, character motivation, excessive exposition, etc.
4. Then I print the whole thing out, marking up the pages with corrections to small errors and identifying bigger issues to address. The things I tend to notice on the printed page:
1. More typos and grammer errors
2. Repeated use of words
3. Continuity errors. 
4. Flow of the story.
5. Then I let it sit for at least a month, and work on other writing.
6. Then I reread the whole thing again, primarily focusing on bigger story issues and more places where I need to show instead of tell. I’m also addressing plot issues here, character motivation and development, etc.
7. Somewhere around here, I pass it around to my beta readers. They are a half a dozen people who read it and give me feedback. I correct issues they identify. These are different than my first readers: I have two or three people I give it to very early on, just for encouragement. They do give me some feedback, which I welcome, but I’m not dependent on. By the way, unless your mom has some special credentials as a writer or teacher, consider your mother a first reader, not a critical reader.  Of course she’s going to say it’s great. 🙂
8. At this point, I’m comfortable sending it off to agents/publishers.
9. If it’s not accepted by anyone, and I’m going to self-publish, then I keep going:
10. I then send it to a copy editor, and correct issues they identify. I don’t have the budget for a professional copy editor, so I pay a friend who is a creative writing major with about six years of solid writing experience.
11. Lastly I give it to a proofreader. Again, I don’t have the budget for a professional, so I pay a different friend, someone who is extremely detail oriented and focused with a good command of English.