Customer Loyalty Rewards Programs
The kings of customer loyalty programs are casinos. The giant Harrah's casino chain has a "Total Rewards" program that offers free casino rooms, meals and entertainment to members. We're not heavy gamblers, but twice they've given us free 2-night hotel stays at one of their Atlantic City casinos. We earn more "comps" toward meals and gifts while in the casino.
Probably the only business that can afford to offer such big incentives to repeat customers is a casino. Your little retail store doesn't have to go so far -- emulate the bookstore and come up with a simple way to get your best customers to come back more often.