I've been trying to do my own promo for a few months to no avail, so I looked up PR firms, which led shortly to this article. I see that I don't have the money for PR that I want today (though it does not cost too much to get more than I had hoped for), but this article had some great insight into the landscape of publicity. And the Redboot interview here links to some other good resources.
I don't know how relevant this is to many of you, as I know a lot of us are hobbyists (good thing this is in the sideroom, I guess), but I feel like I see a "How do I get plays?" thread here every few weeks and this should pre-empt a fair number of those.