I usually teach an Introduction to Automotive Technology class. The first day is usually kind of mixed with students that think they know everything already and students that have the look of "what did I get myself into" on their face. I am usually very thorough in my explanation and give longer then normal breaks so that the unsure students will ask questions. If they don't, then I still try and joke around with them to get the to feel more comfortable and eventually ask questions. It has seemed to help thus far and the self doubters usually end up being my best students in the end.