As someone who has been on TechCrunch many times, I offer the following observations:
1) There are a glut of startups. The only time the majority of startups get coverage is a money event (funding, acquired, dead-pooled). You chances of launch coverage if you are not funded is pretty low. But fight the good fight!
2) Do your homework on the editors! If you just send an email to tips@techcrunch.com, you're going to get routed to a random editor who may or may not be interested in what you do. Take the time to find the most likely editors and email them in advance.
3) There's an old VC trope: "If you want advice, ask for money; if you want money, ask for advice." In this case, I would modify it to "If you want silence, ask for coverage; if you want coverage, ask for advice." Get an editor interested in what you do before asking for the money shot.
4) Take the time to develop relationships with editors. You're in this for the long haul, over multiple companies, right? At this point, I can probably get coverage from Mike, Erick and MG, because they know me and trust me. Conversely, I only ask for coverage in rare instances.
In the short term, #2 is probably most important. In the long term, it's all about #4.