I know that audio books sell great for traditional published authors or best selling authors but I don't believe they have helped too many self-published authors. My advice is to zero in on things other self-published authors might be doing that works for them. Ask some of them (ones that are actually selling and seem to be doing okay in self-publishing) for tips. Also, you can check out John Kremer's book and his sites. His tips help all authors. I'm traditionally published and I find his tips are great for all authors. Anyone can benefit from promotional tips no matter how they are published.