When you deliberately court the attention of the press, speak in a language we understand. That doesn't mean you need to write a formal press release (we ignore 95% of press releases anyway, for reasons that have nothing to do with open source), but do explain in an e-mail message to journalists what the software is, what the announcement means, and why the editor's readers should care about it.
As my old friend Alan Zeichick says: "We don't have the context to immediately 'get' the importance of what you're doing. Be sure to explain it to us."
This doesn't mean we're idiots. We try not to be. But you've gone deep with your project, and I haven't. I may not be familiar with the problem that it aims to solve. So tell me about it.
Another point in regard to attracting media attention: Don't limit yourself to the open source tech press. If your software solves a problem for left-handed oboe players, then it's at least as important to inform the journalists who write about left-handed software (proprietary or otherwise) and the writers at music magazines. (You might have to tell the latter what "open source" is, but at least you don't have to explain "woodwinds.")
It helps to be charming and friendly. It helps even more if you demonstrate that you have a clue about my publication's audience or what I've written about previously.
Also, gain some empathy for the journalist's point of view. Recognize that we are on deadline, which for most news journalists means posting the article within a couple of hours and for feature authors within a couple of days. If we ask for input, or a quote, or anything to which your project spokesperson (you do have one? yes? please say yes) might want to respond, it generally does mean, "Drop everything and answer us now." If the journalist doesn't give you a deadline ("I need to know by 2pm"), it's okay to ask how long you can take to reach the right developer in Poland, but err on the side of "emergency response." It's unreasonable, I know, but so are our deadlines.
It's perfectly fine — and appropriate — to ask the journalist you're corresponding with about the type of article she's writing, which may guide you in the depth or nature of your response. A news story is mostly "what happened, when, and the implications" while a feature story or blog post (which incidentally is what I do most often) might address a meta-question.
Please treat journalists with respect. And encourage the community to do so, too.