Clean up tables after customers finish their food.
Runners are the gophers of the film and TV set, as in “Hey Runner go-for this, then go-for that.” In other words you are the errand runner, the coffee getter, and the general extra hand to finish up chores. This sounds unglamorous and it is. It is an either low or unpaid position, the bottom rung on the set food chain. However it is also an extremely competitive position because it gets your foot in the door of the entertainment industry, which is a very difficult thing to do.
Your daily tasks are to help anybody who needs it, and as a result you end up going everywhere. This is great for just starting out with your career—if you want to be a Sound Editor, for example, then having experience in the editing room is incredibly valuable. Even if it is just cleaning up.
So though you have a rather thankless job, you will get to know a film set and how it operates. You will meet potential colleagues and bosses, and hopefully make an impression on them with your hard work and dedication. Consider this, then, as paying your dues to become a Film Producer, Film Director, Production Designer, or whatever else you ultimately want to be. You won’t hold the position for long, and it is a great way to get your face seen and name heard.