There are several things I've learned in the last year that will help with any future books I put out, and I hope some of those tips can help you as well.
1. Love your cover. No, seriously, You should see the first cover I had on Stolen Luck. Google it and I'm sure you'll find it. Why did I go with it? I wanted the book out now. I wanted a book available for Christmas and working with that cover artist was difficult, so I dealt with it.
Don't deal with it. It's your book. Your baby. Make sure you love the cover because you will be selling your book to other people and you don't want the constant reminder. Believe me. You could be stuck with evil leprechauns for the rest of your life.
Lucky for me, my publisher didn't like it either and was relieved when I told him to change it. While it still doesn't fit the genre, it was a million times better than the original.
2. Don't rush. Make sure edits are done well, covers are what you want, and everything is ready before you hit the submit button. I am constantly rushing into things and I regret it later. I'm thankful for those around me that remind me to slow down, enjoy the ride, and be happy with the better results.
3. Read the contract. If you go traditional, know what that contract says. I am currently in the process of getting my rights back on a series, and a few things in the contract that I figured I would never have to deal with are the biggest obstacles right now. Find someone that knows contract law and make sure you're not making a huge mistake. Look at the right of first refusal, royalties, buyout options, and responsibilities for both you and your publisher.
4. Don't stress over things you can't control. Cover artists need time to create, editors need time to edit, formatters need time to format, and even printers need time to print. Take a deep breath and realize they're doing their best to make you look good.
5. When marketing, don't burn yourself out. When Twist of Luck was released, I went all out on a huge blog tour, and I didn't see a lot of return. It was still fun, and my readers enjoyed it, but I was totally burnt out at the end. Look around for fun ideas and research to see what marketing works now. My friend just did a Twitter party and it seemed to go very well. There are also Facebook launch parties, blog tours, cover reveals, and physical launch parties. Do all of them or do one or two of them. Know your schedule and what you can handle before pushing yourself into it.
Here you go! Good luck with all your publishing ventures!