Offer a reward for customers who buy something from you and show that they checked in at your business on Foursquare using their mobile device. When they do this, they’re telling everyone in their network that they’ve done business with you. Each month, reward the person who gave you the greatest exposure by offering a discount, and asking for their email address.
Providing quality content that will genuinely HELP the reader is a very important aspect of building a relationship with your list. Don't be pushy about the promotion of your products. Sending out quality content within your emails will entice the members of your mailing list to open your mail-outs on a continual basis and actually read your emails. When they read, and like the content, they'll read again, and again. You want to build "TRUST" between you and your members, so don't bombard them with too much of a sales pitch!
You can use this strategy to your advantage and increase your email list by giving people an incentive in return for their email. The giveaway could be free access to an e-book, a report, a gift hamper, or perhaps a lucky draw where people enter their emails and get a chance to win. A tantalizing offer is all you need for people to comply. For example: