Privately held Trader Joe's is highly secretive and doesn't do interviews, so Fortune did some digging around to see what makes the retail chain such a success.
A ringing bell instead of an intercom signals that more help is needed at the registers. Registers don't have conveyor belts or scales, and perishables are sold by unit instead of weight, speeding up checkout. Crew members aren't told the margins on products, so placement decisions are made based not on profits but on what's best for the shopper. Every employee works all aspects of the store, and if you ask where the roasted chestnuts are he'll walk you over instead of just saying 'aisle five.' Want to know what they taste like? He can probably tell you, and he might even open the bag on the spot for you to try.
Customer service, pay people well, and trust them to do good work. That and be clever about what you sell and to whom.