Well, the first is to look for grammar mistakes, try to read your novel out loud at least once for sentence structure (I don't do this with my smut on SH but I do it with everything else I write).
Second part of a rewrite is usually based on feed back from other people, or things you felt you needed to rush. Writing is subjective, just because you like something doesn't mean others will and there are many different audiences as well. Re-writing something usually is to expand on a character, focus on something more or eliminate parts that don't add to the novel.