When I prepare for a new class, I do my best to read the material, take a look at the power points and take my time on the prep if I have the time to do so, I cannot be unprepared, if I am unprepared then I feel that I will not only let my studnets down but also myself. This way if I am prepared then I know what I am doing and I let my studnets believe I know what I am doing even if I don't, and I never let them know that it is the first time I have ever taught that particular class.
