From what I've been told, offering an attractive lead magnet is the best way to entice a signup. This can be an ebook, checklist, webinar... I am trying to build a following for my first book on brand identity for small business coming out on May 20 on Amazon, where it will be free for 5 days. I created a free pdf summary of the first section of the book, which I am about to start offering for free as well as a webinar on the subject taught in the book.
Something like this might work for you: https://drive.google.com/file/d/0B6X...ew?usp=sharing