When and how often do Startups need to do Press Releases?

At what times do you suggest doing press releases for startups

• Before a product launch ?
• After a product launch ?
• After the customer base has reached a specific number ?
• When you have new investors or investments ?

Journalists have rather simple rules what makes an information newsworthy:

• Prominence : The information involves a well-known person or organization.
• Currency : The information is related to a topic a lot of people are already talking about.
• Impact : The information affects (or may affect) a lot of people. This includes direct and indirect effects.
• Conflict : The information has some kind of disagreement between two or more people or parties.
• Weirdness : The information is unusual or strange ("Man bites dog").
• Timeliness : The information is about an event that happened recently. 'Recently' is
  defined according to the publication cycle of the media.
• Proximity : The information is about an event that happened somewhere nearby. 'Nearby' is defined according to the distribution of the media.

A "lot of people" often just means a large part of the audience of a certain media.

Basically any event that fits one or more of the above criteria is newsworthy for some media and you can make a press release about it.

Hope that helps.

Press releases in themselves are not very valuable. Most new media doesn't care anymore. If you blast a press release on the wire, it most likely won't be picked up by anyone.

A better approach is to target very specific media and make sure you have some kind of relationship with them. You can also learn about exclusives and see how the business of making news works. That helps in understanding how journalists and bloggers pick the stories they cover.

To answer your question: communicate when you have news. First product launch is definitely a major news (look at the TC50 and DEMO events if you doubt that the press cares about first launch). Investors is also news worthy, but with a more professional target (your endusers don't really care that you got funding).

Again, the key test is whether it's newsworthy. If it is, communicate.