Mat Reive, High School Mathematics and Computer Science Teacher
In my high school math classes, it is common that I start the class off with a brain teaser. This is usually a brain teaser puzzle from either ThinkFun's Visual Brain Storm set, an Ivan Moscovich or Martin Gardner book, or a brain teaser that I have gotten from the internet. The whole class participates and gets engaged in trying to solve these puzzles. If I ever forget the puzzle at the start of the class, they always remind me.