As a former journalist and 26-year public relations veteran I have found that the first criterion is whether you are ready for "prime time." Many startups operate under the mistaken notion that they have something newsworthy for a journalist to cover. For example, they issue a press release about a new website or a non-key hire. Before reaching out to journalists, have your funding, strategic plans, market research, production and personnel in place, then be ready to explain why your startup is "news" and should be covered. I'd be happy to expand in this in a call.