I had a teaching mentor who suggested that a teacher should always have a cup of coffee or water or something else to drink in class. The purpose was to have something to do after posing a question that no student seemed particulary interested in answering. As the awkward silence drags on, the teacher cooly sipping his drink gives no indication of a willingness to bail the class out by giving the answer. Someone will usually step up. During those moments, I can't help but have the final jeopardy theme from the TV show running through my head. I always wondered if it would be useful in class. Now that I am using clickers again, I may try it to denote the clicker response time.