In an undergraduate chemistry class, I had an instructor walk into class with a canister of liquid nitrogen and pour it out onto a plant on the floor. After the cloud of gas disappeared, he snapped off a bit of the plant and threw it onto the floor. We all watched in amazement as it shattered on the floor. Through this process, he never said a word. As soon as our oohs and ahs subsided he began presenting the course material. I have tried to adopt a similar (yet less dramatic) approach to the first class meeting. A simple demonstration of a task that the student will eventually become proficient at has served as a good tool to generate enthusiasm and get students in the mood for learning.