One of the far best methods to get attention without having to pay for it is simply to run a contest. There is no need to give away prizes for several thousands of dollar, but it will help, since you will get attention just by giving away cheap prizes such as a DVD or a interesting book.
How to get subscribers
There is no point in forcing your participants into signing up for your newsletter since most of them will cancel their subscription as soon as the contest is over and you have chosen a winner.
Instead you should add a simple checkbox at the bottom of your form.
Subscribe for our free newsletter and receive information on upcoming competitions here at [blogname].
When the contest is over you simply gather all of the addresses, who checked this checkbox, and add them into your preferred email software.
Make sure to read the rest of my posts about creating a successful newsletter.