Hi, I have been running a blog for around 1 month and wasn't getting to many hits and I wanted to build more of a community. I then decided I'd add a mailing list, so I could let people know when the site is updated. I added it, then nobody signed up, so I was reading this site and it said add an incentive. I said I would randomly select an email address in a few months and send them some free goodies through the post. I posted this in a few forums and I have got a good targeted mailing list. I just thought I would let people know my experience if anybody is thinking about it, it really works!
I'm not sure what's the best ways, but I had started getting signups to my mailing list the other day. I am getting on average 1 - 5 emails a day from just having a form on my site. I am not giving any incentives or anything. If people want the information sent to them via email then they will genuinely just signup anyway. Although 1 - 5 signups is alright a day, I would prefer a few hundreds a day as the more you get the better, but I would not do it the wrong ways.
Run a multivariate test with some copy around that box. It's a little unclear how to sign up, why you should sign up, and how to "submit." Might be a few more submissions.