I've never been able to get attention from any kind of blogs (although when I attempted, the list of blogs I contacted was small, and the blogs themselves were big).
I also didn't send out any press releases.
I got my followers on Twitter to retweet my app, and despite having maybe 40 or so retweets, only 1 seemed to convert to a sale.
The biggest and most common weakness through all of these has been either not having a website, or having a very basic and crummy website. That has been my lesson so far.
I don't consider myself to have failed. I consider myself now knowing 3 or 4 ways how to not get promotion. As I said, the biggest problem, I feel, has been a weak website presence. The apps themselves, while not stellar, I would certainly put them in the "Good" category.
Though unfortunately all of them are currently quite out-dated.