I took about 2 weeks to put together a guide on how to collect emails at the prelaunch stage (but could be aimed at campaign owners who have a live campaign and want to get the word out).
I identified running a competition is a great place to start, especially as an incentive to get entrants to do something for you in exchange for the prize (Such as posting about you in their social network and joining your newsletter list).
Another is setting up a prelaunch page correctly, who to target and what to do next.
Enjoy and feel free to leave any comments/questions on this post:
http://www.linkedin.com/pulse/how-collect-100000-emails-launch-successful-campaign-giles-dawe