Okay, so it might be a little weird that I'm posting success tips, when I haven't actually found real indie success myself. However, once I add my SmashWords affiliate sales I'll be right around 200 sales for August, so that's not terrible either. So, here's what I've learned in the last year or so:
1. Use a professorial editor and then at least one professorial proofreader (I've started using two) - Indie books get a bad rap for being poorly edited--that's because many are. However, with one exception, every successful indie author I know goes to great lengths to produce an error free manuscript.
2. Get a great cover (see examples: http://www.mjaware.com/covers/med.jpg & http://www.mjaware.com/covers/GirlsBite.jpg) - You don't have to spend a lot of dough. Here's two low-cost cover artist I recommend: XXXXXXX and Rebbecca Weaver. Rebbecca does great photo manipulations and she even does the cover layout too.
3. Get reviews (if most are not positive your probably DOA) - This one is a harder than you'd think because a lot of bloggers won't review or even deal with indies. This week I've e-mailed two dozen reviewers, asking for a review or even just an announcement of my upcoming release and I offered to give away a free print copy of SZJMB to their readers. However, only five have replied (I'm sure more will) and only three of those are going to review (the other two graciously offered to promote with a giveaway).
4. Write a great description - Your cover gets a reader to click on a title, but the description gets them to purchase (or at least download a sample). Make sure their are not grammar errors (this means have someone else check it for you) and keep tweeking it until it sells.
5. Marketing and promotion - Besides reviews you need to start a blog, Facebook, or Twitter account. But don't do all of them just cause you have to. For example, I don't do Twitter well, so I skip it. But I just opened a Facebook page(Got a minute? I only have three 'likes'). Believe it or not commenting on other blogs and posting on message boards helps sales too (the messages get indexed by Google and show up in search results). Just make sure you stay civil.
And number 6.... Keep writing, of course.