The cheapest way to discover if a startup idea will make money
maxkle.in
maxkle.in
I think if you are going to use twitter, have something interesting to say about the area where your startup is based in - that will attract initial early adopters and those who are passionate about the space.
Also, I do feel if you have some JS, CSS knowledge, go out and actually build a landing page - see if people actually sign up to what the product will be (or could be) - that's a much better way to gain traction and email addresses for those who could end up being your early adopters.