Understanding the emotional and logical mental processes of your readers is the best way to take your email sign ups to the next level.
Make them feel part of an exclusive group. Use direct and compelling language. And overcome as many objections as you can.
If you can do these three things, you will grow a steady list of subscribers that can be a source of online income for years and years to come.
Read this article on Copyblogger to find out exactly how to do this.