I know that when submitting a manuscript, it should be my best work.
It really should be. I once sat in to listen to a panel of editors from different publishing houses. A question was asked, 'how long do you read a manuscript before deciding whether to read further?" The first editor responded, "I always read three chapters. It takes me that long to get a feel for the plot and the author's style." The second editor said, "I read the first chapter. By then I know whether I want to read further." The third editor sort of hesitated then said, "I read three paragraphs." There was a collective gasp in the room. She hurriedly added, "I really can tell by then whether the author has hooked me." So we can't hope for the editor to give it until chapter seven when things start rolling. They're busy and I'm betting most these days will not read past the first chapter, if that, if it doesn't grab them.
I've wondered how much editing goes into the process once the editor gets to work on a manuscript. Do they revise plots? Add threads? Or do they work with the elements already in the story to improve them? Does it depend on the editor?
It really does depend on the editor. Every once in a while I'll hear horror stories about editor intrusion, and how books are turning out to fit her vision rather than the author's. I've worked with 8 editors at Silhouette and one at Berkley and they've all been wonderful. An editor might suggest revisions; if a scene doesn't work or she wants the story to be more emotional, or soften the hero (I was once told my hero was 'too mopey' LOL), that sort of thing. I haven't had to do revisions on an SRS in so many years it's difficult to recall the last time. But when you get revisions it can be two or three points or it could be 3 pages of bulleted paragraphs detailing changes they want. Two of the points might be major enough to cause me to have to think hard about how to execute them. The others are minor, like they don't think the female cop would have long fingernails ;) Things so minor that they would have noted them in line edits if they weren't sending the revisions.
That said, editors don't revise plots. They make suggestions for changes for the author to make. And the changes aren't written in stone. You talk to the editor about them and maybe explain your reasoning. Often times it's a situation where maybe I wasn't as clear in a point as I thought it was, so her questioning just makes me clarify things in the manuscript. They can certainly suggest you add threads. If there are things the author isn't willing to do, it's usually a give and take and compromise.