One 'gimmick' that my fav LGS in the Chicagoland area uses is the 'buyer's card'. Whenever you spend $100 at the store ($10 at a time) you get a $10 gift certificate. After you've filled a card ($300) you get a $25 gift certificate along with the $10 for finishing the last row. This also included secial orders as well as normal purchases. It's worked well for them for many, many years (and a fair bit of my cash). Repeat business is the key to success in retail and they defiantely have it.
Customer Loyalty programs do work, just check out Games Plus in Mt Prospect, IL.