After mentioning how much time I spent editing my books, like the whole summer, I thought it might be of interest what that means. Assuming you are doing your own, cannot afford to hire a professional editor, as best I know it, there are various ways to approach the job. I'll discuss two.
A writer can literally edit each chapter as they go. Write a chapter and go at it word for word as they write. Make sure each word/sentence/paragraph/page is polished before going onto the next. Have an outline nearby and stick to its basics. If they vary from it, they have a good reason and create a new outline.
If such a writer has a beta group to check what they are writing, they'd write that chapter, probably still trying to keep it right for spelling, punctuation, consistency, etc. Then send it off to their readers or even their editor-- while writing on the next chapter. When it comes back, they will take into account what the beta readers thought, if there is a majority opinion and, if it was also sent to an editor, what they suggested. Use what works and argue about what, as the writer, they believe did not.
Basically chapter by chapter editing, with or without beta readers, likely means the book is ready to go out the day it's finished.
There is another approach to editing, and it's mine. It's how I used to paint and sculpt also. Write it in a white hot heat of feeling the energy of the story. Don't worry if it's perfect, although for those who tend to write with grammar as a natural part of their writing, it's not going to be totally unreadable. Basically this approach captures the characters, the plot, much of the dialogue. For me, those aspects usually end up being what stays with the book.
For any book I have ever written, I had spent a lot of time thinking about it before I ever start writing. I know the characters and what I want them to be. I know the plot. What I have fun with along the way are the things that crop up, which I didn't expect. That doesn't keep me from the ending I knew it would have. The ending can be tweaked, but the gist of it won't be different.
Ideally I set my rough draft aside for a couple of weeks and work on other projects. It's hard to do an edit when you literally just finished-- it's too fresh.
Some writers have a different purpose for each subsequent edit. They look at specifics like say spelling or logic, etc.
My approach is that I go for the polish whether it's the first or the seventh. I look for typos, punctuation that is missing, and the long blue line that Word uses to say a sentence is not correct. I always check out Word's opinion, but sometimes they are wrong especially when it's dialogue. In editing, I look for consistencies of timing and character behavior.
If in editing the first time, I can enrich a scene by more details; or if it had too much detail, I'll add/delete it there. The future edits are less likely to add but might still end up with deletions.
Edits are also where I double-check my research when I come across specific points where I can see there might be a question. Literally I don't write anything that I haven't researched first, but sometimes I've forgotten the details, and I look for my notes or go back to the original source to be sure I got it right. This is true for historic, of course, but also contemporary. There are a ton of ways to goof up even a contemporary.
With each edit, I look for where I can enhance the action. This happens a lot with 'said' where it is better to insert the accompanying action instead. It still must make clear the character speaking.
Editing also looks for consistency in thinking. I don't have this happen often but if say a character has a fear of snakes and the next chapter is handling one with no fear, that doesn't work. Likewise I ran into one, early on, where I had a heroine who didn't like coffee and then had her drinking it one morning on her desert patio. Definite no-no.
Recently, when I had edited a rough draft that I had written in one lunar cycle, I was very upset that on the sixth edit, I still found redundancies or places I'd gone on and on. I had not expected that. For awhile, it gave me some doubt about my writing ability, but I looked at the characters, dialogue, plot, conflict, the WWW, and felt overall it was all I wanted it to be.
The characters and story warmed my heart where I wanted it to do so and made me feel the action. A writer has to find all of that in their own writing or there is no hope any reader will. If reading it to edit makes me lose interest in the story or feel it's blah, it probably means the book has a bigger problem than punctuation.
