The basic outline of our strategy:
First, start with the awareness and PR of the project, Facebook is where I would always start, get the page ready and looking good, consistent content about the project, the features as benefits selling etc.
I also run Facebook ads, to send traffic to a dedicated landing page that grabs emails for early bird special offers. This is for the email marketing that will happen close to and after the launch date.
For clients I would say the most important thing is the consistency, staying active on the social platforms and always be collecting emails to market to at a later stage.
All pretty basic, but as you can see it will bring great results, just check out
Oddball, our latest client to launch.