For me, at least, this rule works at almost every level: if something isn’t working, prune it.
If a sentence doesn’t read well, take off any preposition phrases at the end. If that doesn’t help, strip every word out of the sentence that you can possibly do without, and then start putting things back, one at a time, until you get back a sense of balance.
Paragraphs are odd things with a rhythm and reason all their own. In fact, multiple rhythms. Well structured paragraphs move the reader along a smooth path; choppy paragraphs don’t. (Sometimes you need choppy, for stylistic reasons; I’m not talking about that here.) The flow of multiple paragraphs on the page is also important. If the scene isn’t feeling balanced, print it out. Hold it up at arm’s length and look. Lots of big, blocky paragraphs? A whole squadron of short, choppy paragraphs? these things should tell you something. Of course, a nice balance will help the scene move, but it’s not a guarantee that the story will work.
Because sometimes stories don’t work. More often than not, something is off. Out of balance, off kilter. This is where the real pruning comes in.
I have heard it said that the first thing you have to do with any manuscript is chop off the first page or so. Oddly enough, it’s true sometimes. The writer starts writing, but the story takes a while to click into being. This happened to me with Homestead. The only major edit was that I cut the first two scenes in the first story, and the whole thing immediately took on a new energy.
It’s often true that the writer can’t let the story go and so it drags on. I stop and ask myself if I need the last paragraph in the chapter I just wrote, and about half the time the answer is that I don’t.
Someplace along the line, many of us got the idea that flowery constructions and long descriptions make good prose. And sometimes they do, but more often they just get in the way.
When I’ve stuck too many characters in a scene, it sometimes comes to a grinding halt and will only start up again as I toss people out of the room. Why exactly Peter is sitting there? No good reason: out with him. Stripping extraneous characters from the scene can give it — and the writer — a tremendous boost of energy.
Finally, this thought: some people hate to cut anything at all, because every word is written in blood. I can hear my students wailing still: but i worked on that opening scene for HOURS. Sometimes you have to let things go, no matter how hard won they were to start with. If it kills you to do it, put all the little snippets into a file someplace and give it a name you’ll remember. You can have a look at your snippets file when you’re trying to get a sense of where to go next, and sometimes you’ll find the answer there.
Sometimes I pick up a novel and just look at the way the sentences and paragraphs are structured. It’s an interesting exercise and quite useful.