Sometimes it is as simple as changing the format of a lesson, or altering the layout of a classroom. Sometimes it is to introduce a new approach or problem where students need to take an alternative role. I often create chaos and uncertainty in my lessons. People are not comfortable with this, and will do anything to resolve it into something meaningful. The answer is always, always keep them guessing - and then send them out confused, if you have to.
Via Gust MEES