How to keep busy in the minutes between orders?

I just started a new job at a local coffee shop and I am really stoked. The problem is, the boss is really tough, and hates it when people stand around, and will yell if he sees people doing so. There are a lot of prices to memorize, so I feel really overloaded already. Since I am new, I'm not familiar with all the busywork that should fill the minutes between drink orders, and no one seems to want to tell me all the things that need to be done in the downtime. So if I stand there for 10 or so seconds brainstorming on things to do, then the boss thinks I'm standing around and will yell at me. The only things they've told me how to do is stock cups, fill the espresso grinders, and wipe things down. Any ideas of what other things need to be done at a coffee shop to spare me being yelled at? Obviously I will figure it out with time and experience, and I won't be standing around once I know the ropes, but until then I just need some ideas! Anyone?