There are two things that will make your book successful:
What you need first and foremost is readers. So you need to build a platform. See the books by Michael Hyatt, Jeff Walker, Guy Kawasaki, and others* on the subject.
In short, what you need to do is have a website, start to blog, connect through Twitter, and generally brand yourself and network with prospective readers through social media. Ideally you would have already done all that while you were writing your book, so that now that it is finished you could simply mail out a newsletter or post a Tweet with a link to the finished product.
The second most important thing is that you quickly write your next book. Books sell each other, and a happy reader not finding another book by the same author is one reader lost.
All bestselling authors have a score of books out there. So sit down and start on the next novel and publish that within six months to a year. And then the next.
Obviously 1 and 2 take away time and energy from each other, which is why successful authors either have a publisher who takes care of marketing, a husband who takes care of marketing, or pay someone to take care of marketing. There are very few successful authors who do all of this alone, and most can only do it alone on the basis of past success from publisher-published books.
* All these books contain about one page worth of useful advice, and this advice can be found freely on the web, so don't buy the books. I'm just naming these authors so you know who the popular authorities are and were to start googling.