We have used a “Bingo” card in the past with success. The servers would “X” off a given square when they sold the item listed, be it entree, dessert or starters. Each “Bingo” would pay something small, but interesting like $5.00 or a small gift card. We don’t use it often so it keeps the game fresh, but it’s been highly successful and the servers really do get in to the “competition”.