edit: I was thinking about how to award good employees and I think it's simple: give a small paper form at the end, where people will provide ratings for the service provided. Not all of them will fill them, of course, but I think you will get some feedback about who are your best employees and who are the worst. Also, regarding tips, how do they help the kitchen staff (in the restaurants, you can find other examples on other businesses)? That sistem isn't fair.