I can usually tell which sections of the manuscript need the most revising. It's a simple technique.
(Please keep in mind - This works best for me when I'm revising, but every author has their own method.)
The scenes that I've gotten right feel a lot like running once you've found your stride. My eyes just race over the page. It's almost like I can't wait to find out what happens next, even though I was the one who wrote it. (Actually, these sections are the parts most likely to have typos, because I read them too fast. That's why I make myself read out loud to make sure that I slow down.)
Unfortunately, this doesn't happen with every chapter.
Sometimes, I find myself stumbling over words. That usually means that sections has whole sentences that don't need to be there. So, I delete them and continue on my merry way.
Sometimes, characters say or do something, and I find myself wondering why on earth they would do/say such a thing. That's a real problem. If I think that, then a reader definitely will. Usually, this means that I need to re-imagine a scene. That can take days, weeks, or even months. Or it comes to me when I'm trying to do something completely different - like sleeping or washing dishes or making coffee.
Anyway, I'm halfway through revising this other manuscript. Since I read through it a couple days ago, I realized that the first half of the manuscript is in much better shape. The second half needs me to re-imagine at least three scenes.
My goal is to turn in as clean a manuscript as possible so that my editor(s) don't have too many glaring structural problems to bother with. I don't want to be one of those authors who has to go through eight revisions to get it right, so the poor overworked editor is quietly pulling her hair out in her office/cubicle. I have seen this happen. It's frustrating for everyone. (Sometimes, editors even blog about it.)
Back to tackle scarily clunky scenes...