In one of his essays, Terry Pratchett says something to the effect that the first draft of a new book is where he finds out what the book is about. I found that really helpful and it makes it alright that sometimes a first draft is all over the place. In particular it gave me a point to focus on that helps me analyse the first draft. In that analysis, there is sometimes the point where I say "that was a good scene but it doesn't belong in this book" - can use it in another one. And once I find out what the book is really about, it helps focus other things. Now this is all pretty waffly and vague - so a few details. I write sff not non-fiction so when I say what the book is about, it is not just the main story, but the underlying things as well - I try to be multi-layered (a bit the way Terry Pratchett is) - as in you have some form of adventure aka crisis and you have characters. During the first run through I am meeting the characters and sometimes they undergo massive personality changes through the course of the story - not in a personal growth way, but in an oops way - the book and characters changed as I wrote it and by the time I reached the end, there is drift from where it started because I had bright ideas (or not so bright one). So on the next read, it is identifying all the inconsistencies, identifying what I want from the story and adjusting.
I've only really recently consciously recognised the "what I want from a story" thought - I read widely in sff but have gradually worked out that what I want to write, is not nearly as wide as what I'd be happy reading. I have had periods when the writing isn't working for me and I have a really uncomfortable feeling about it, and have finally learnt that some of that is that it is not a story I am happy writing. It may (or may not) be a perfectly reasonable idea and would slot well into the SFF genre - but there is something about it that either makes me uncomfortable or lacks zing. One of the things I've recently identified is that I like writing about competent people who work well together, or who make an effort to work together (even if they wouldn't be buddies if they didn't have to work together) and also people working to make things happen. So when I have book ideas, I step back and look at them and say "well yes, but does it have the core things that are important to me? and if not, since I like the story concept, how can I write it so it does have the core things"
Another thing that can be useful is when you finish the first draft and spell check it, put it aside for a few months before you read it again - and do something else in the meantime. Just occasionally when you are reading it fresh there can be bits where you say "actually this bit is pretty good" - as well as all the bits you can see are not so good. But it is a wonderful feeling to read something of yours, even if it's only a few pages and go "hey, this really flows".
And one day, I will actually reach the point of sending a polished manuscript out - but not quite yet.
So not a great expert..... Incidentally, I find beta reading/critiquing other people's work help hone my analysis skills on my own work.
