I've seen various posts about how to denote sections of a WIP that are "done" and not to be further fussed with. Font colors, font styles, separate files, etc. Once a section is done, it should be set aside until the next full read-through and revision of the book. The tools available are quite different now than in the days of quills, fountain pens, Underwoods and Selectrics, but the need remains for knowing where you are in the thicket.
I must admit that my own method is no method at all. When I feel like a particular chapter or scene is good enough, I just go on to another part. I save files in labeled folders with incremental version numbers:
New Book/intro 01.doc
New Book/intro 02.doc
New Book/Sammy kills Will 03.doc
New Book/Will meets Carol 02.doc
If I were more organized, these would be in some kind of uber-structure of chapters and scene, but I'm not there yet. Within the files themselves, no visual cues denote one stage of completion or another.
When P.G. Wodehouse was working on a book, he would thumbtack typed pages for each chapter in a line all across the walls of his study. For scenes that weren't working he would move those pages lower - the worse shape they were in, the closer to the floor. As the revisions took hold, he would move the revised pages up, until they reached a spot over his head. When each chapter was at that upper point, he declared it done. When the whole book reached that point, off to the editor it went.
One of the most prolific and artful humorists of the 20th century, Wodehouse's characters, such as Jeeves and Wooster, live on in the original and as archetypes. His novels and short stories are solid sellers to this day. However, his letters reveal that he was constantly worried about having run dry, that each book he was working on would be his last.
His prose reads like it's effortless fluff, floating across the page like a wisp of cotton candy that escaped the carnival. Yet the craft and sweat (and fear) that went into the work was tremendous. That's a wonderful example of dedication and work ethic, even if it's a pretty high mark to compare oneself against.
I saw some advice once that in trying to break into fiction writing, you should consider only living writers as role models. The idea is that the publishing biz, along with the tastes of audiences, will be quite different now that it would be back in the days of Austen, Dickens, Twain, Hardy, Woolf or Asimov.
Wodehouse having died more than 30 years ago, he's ineligible. If I had to limit myself to a living author who's writing I admire (and whose career arc I wouldn't mind having), it would probably be Michael Chabon. I wonder what method he uses for knowing how to move on.