You don't have to make every Tweet about your blog posts. I would first try engaging your audience, since Twitter is a social network. For example, try tieing in your Tweets with current hot and popular topics then you are more likely to get yourself noticed; especially since these topics are already on people’s radar. As such, when you post something on these topics it will most likely stand out to them and drive them to your site. You could also create a squeeze page specifically for your Twitter followers to capture their email addresses. It would be a good idea to offer them something of value (i.e., free eBook, free report, etc.) in exchange for their email address. Be sure to offer them a privacy clause concerning their email since people are reluctant to giving their email because they don't want to get spammed. You could use Socialoomph.com to send a direct message (DM) to all your new followers which will send them to your squeeze page. Hope this helps.