Lewis Howe's said on his podcast "School of Greatness" that if he had to start over again he would start with building his list before anything else. How would one with no platform go about building an email list?
Tactically you could set up a one-page site using populr.me linked to a Google docs form to collect email addresses. As Bruce mentioned, ideally you would have something to offer in exchange for people providing you with their email address, but you could also have the page be a teaser of what's to come and have the users subscribe to get updates on your product launch, new content, or whatever it is you are building.