The Consumerist has a great article written by a retail games salesman with 9 "insider" secrets. Some are a little more obvious than others (#1 Extended warranties are usually unnecessary) but some are fairly enlightening. Take #8, for example:
8. Employees are ranked. Companies often rank employees by various metrics: the number of membership cards they sell, the number of games they convince customers to reserve/preorder, the number of extended warranties they can sell, their "attach rate" (adding accessories, strategy guides, and other profitable items to games and systems), their ratio of new to used sales, and (especially during the holidays) the number of gift cards they sell. Management will use these numbers to determine job performance, and they can influence raises/promotions/threats of being fired. Some of these items are even commissioned.
via Joystiq