Grow your email list by offering a birthday or an anniversary club. People that sign up get something special that month and you get access to a potential customer. People love free things and if they sign up, they probably like what you are giving them. This means that you will have a list rich with people who are your target audience and rich lists produce more sales. Use your email list segmentation (you had better be with a service that has it) to manage those lists. Then you can send out the special promotion to the right people. Make sure what you give is worth them signing up but not so good it breaks your bank.