I'd second Benjamin's tip, to read your own work aloud. It's very, very helpful for any kind of writing you might be doing. If you can read it aloud to somebody else, so much the better.
I also like doing a reverse outline for certain kinds of writing—including creative non-fiction, if not so much fiction. Purdue's Online Writing Lab has a great guide to how these work. (Link below.)
Finally, said the usability professional, user testing! Show your work to people and see where they get stuck. This one's particularly useful for structure and flow issues. Do proofread first for grammar and spelling, distractions for your readers. (On which: Try proofing from last sentence to first. It can reveal otherwise obscured sentence-level issues.)