Whatever your business sells, you need to make sure you are building your lists.
Make sure your web site or blog has a form subscibers can fill out.
If you don't have a web site or blog, make sure you have set up your Hosted Capture Page in your back office.
Once your letters are set up and your forms are ready, PROMOTE, PROMOTE, PROMOTE! If you don't have an advertising budget, take advantage of all the free promotional tools you can get your hands...