And also the most obvious:
Always have a second pair of eyes to read your novel.
Plain and simple. And also pretty obvious. If you’re going the traditional publishing route, you’ll have a professional editor helping you wherever you need it. But when you’re self publishing, you may not necessarily have a professional editor to assist you, unless you happen to be good friends with one. If at all monetarily possible, hire a professional because no matter how much self editing you do, there’s nothing like someone else’s eyes to show you something you might not have realized was a problem. I say this out of experience.
When I was younger, I always had my mother read my stories, luckily for me, she was wiling to tell me when something didn’t work or didn’t quite sound right and it’s been beneficial to me to be able to have someone else to look at my work. It’s basically, you can’t see the forest through the tree’s. More often than not, the more time you spend reading something the more likely you are to miss what could seem very obvious to someone who didn’t write it. As I reach the end of my personal edits (almost on chapter 20) I’m starting to get what I like to call, editing highway hypnosis. You know when you’re driving on the freeway for a long time and everything sort of just goes by in a blur. You got home but you don’t really remember how because you were on auto-pilot. I know for a fact that I’m currently on chapter 19, but I also know that I don’t remember editing three or four chapters somewhere in between eight and nineteen. It’s sort of nerve wracking not being able to remember what you edited and what if anything was changed, and it really makes me glad that number one I printed everything out and edited it that way so there’s still a chance for me to get a third revision in when I put it into the computer but number two that I’ll have a second pair of eyes checking this over very soon.