Repeat customers like to be acknowledged. One way to do this is by learning their preferences and incorporating them into your service.
For example, I often eat breakfast at a local diner. Kathy, one of the servers, typically asks me, "Do you need to see a menu today or will you have the usual?" It makes me feel valued to know Kathy remembers my order, but I also appreciate her asking just in case.
What do you know about your repeat customers that you can use to provide even better service?