Just to give you an idea of how awful editing/revising can be, this final version of my novel Lunacy went through FOUR entire rewrites. Four. I wavered between the book being from first person or third, then I realized that I couldn't relate to Kacea at all anymore because she was so much younger than I was. For some people, the age gap doesn't matter, but I wasn't a sixteen year old kid anymore when I got serious about things. So I made her a senior, wanting to be able to skip those awkward formative years of being an older teenager, and getting into more adult stuff at some point in the book. I completely changed the way she talked, the way she acted, and I think I made her a mature enough character that I didn't want to punch her in the face anymore. I've had people say "Teenagers don't talk like that. They sound too grown up." To be honest, that's exactly how my friends and I talked when we were in high school. If the intelligence level of society at large has dropped so low that all they can chat about now is the Biebs and Jersey Shore, we're in a sorry state indeed...
I digress. So anyway, I did a total overhaul of the deity and cosmology system. Originally, I'd written the story with some gods I created on my own, but they were half-assed and didn't do it for me. Now, we're totally immersed in Norse mythology, and I've woven it in with my werewolves in a way that I'm proud of and I'm fairly sure is unique to me. Although I've seen a lot of viking-esque tales on the rise, I don't think there's another quite like mine. =]
I've also been doing a lot of research on things to do to make your story sound more polished, look more professional. The basics of spelling and sentence structure are pretty much a given. Grammar... I feel like it's a fluid concept. You can end a sentence with a prepositional phrase and some people will have an aneurysm, but as long as the words flow together in a way that sort of removes you from the words and draws you into the world... I think you're golden. Stephen King is a master of sentence fragments, as is Laurell K. Hamilton. That's something that would have gotten you shot thirty years ago, but now, with so many books written in first person that run on an internal monologue, I don't think it's that big of a deal. There's a difference between someone being a true grammar nazi, and someone pointing out that you can't spell your way out of a paper bag. =P
Brevity is a big thing I'm learning to embrace when I write. During my first round of edits with Lunacy, I cut over 5000 words. Five thousand. Some people are publishing stories that are the length of crap I removed from my novel. Then I went through and found what I call my "crutch words". The words/phrases you overuse the most that add nothing to the story. My biggest ones are: suddenly, almost, a little/a bit, and smirk. Sometimes, just changing that one word brought in another paragraph of awesomeness. A change you think is insignificant can produce great effects in the long run.
So, to give you an example of how much things change for me, I'll give you a paragraph of one of my WIPs. It's a short for an erotica anthology that's centered on steampunk. My title is "Clockwork Heart".
Here's what the paragraph looked like at first: