Getting Customers to Come Back.

How do you get customers to come back to your store? That is a question that even the big retailers and even Specialty Store Services encounters all the time. Is it service? Is it the price of the product? Is it the product line itself? You can get the customers into you store with a sale but eventually the sale ends right? We have been kicking the idea around here these last couple of days and trying to figure it all out. But in the end we have not come up with any answers. Anyone have any ideas?