At the beginning of each gaming session I ask the kids a series of questions and give tiny bits of candy (e.g., a single M&M) for correct answers. Last time we did this I asked rules-related questions like which dice to use for attacks and why we roll initiative. While familiarity with the rules does make for a smoother gaming experience, I think there is potential to use this technique for greater good.
Next time I'm going to start with questions about the words we learned last week.