Set the bar high; students will measure up:

Good students are there to learn and they know it won't happen automatically. My experience is that if you set the bar high, and do NOT waste the students' time with tedious work that serves no learning purpose, they will work as hard as they can to measure up to it. The myth that students want an easy course is just that, a myth. Some of them may complain and moan at the moment over some very tough homework. But at the end of the course, I generally am thanked profusely for setting the bar high. "Thank you, I never thought I could learn so much in one semester" is a comment I often get at the end of the course.