I'd heard this recommended so many times that I feel silly for not doing it more often. I already read most of my short stories aloud to myself, and I catch all sorts of things that, try as I might, I never noticed when reading in my head. As one might expect, it's especially good for dialogue, but it's supposed to work on essays, too. Still, I'd never quite managed to edit any of my novels this way. This is partly because they're long and partly because I don't live alone. Now, I've finally sucked it up and taken my laptop up to my room (or waited until no one else is in the living room area) to read out loud.
Most of what I catch this way is the stuff that's fun to change because I don't feel conflicted about it. It's repetition, unnecessary words, and awkwardness. It's criminal overuse of the word "rather." Sometimes they're sneaky - I can usually avoid using "to" three times in a sentence, but what about (get ready for this) two "to"s and a "two," too? The voice snags on things that the eye may not catch. These things are not in my manuscript because I couldn't decide whether or not I needed them. They are there because I didn't notice them.
Funnily enough, when I read aloud for awhile, my silent reading starts to take on a similar pace and deliberation. I could probably continue to edit that way if I wanted. This seems especially likely given that I find myself mentally cutting and rephrasing things in other books I'm reading. For example, a book I'm currently reading contains a battle scene wherein the protagonist's opponent extends its sword "so as to impale him." So as to? In a battle scene? Really? Here, "so" and "as" are exactly the kinds of words I'd find myself involuntarily skipping while reading aloud, and so would take out during that stage of editing. It amused me greatly to find myself trying to skip them in my head, too. A similar thing happened later in the same book, when another character "still continued to chuckle."
Small cuts can be incredibly rewarding. How often do you get to make changes that seem to clearly, objectively improve the work? For example, I'm astounded at how many unnecessary dialogue tags Rabbit and Cougar still has. And while so far, the technical errors seem not to have survived the last edit, reading aloud is great for catching those, too.
So that's my writing tip of the day: Read your work aloud. It's by no means a new idea - I believe I've actually plugged it on this blog before - but it's a good one. I didn't believe the difference until I tried it. And from what I've seen, very few works of writing suffer from over-editing . . .