As an instructor for general physics one of the questions that occurs to me as I read the reports of research in physics education is: How do I use this new information to help me teach my course? One thing the results seem to be indicating strongly is that it is critical to get the students actively wrestling with the concepts, principles and relations. So I wonder what kind of tasks and exercises I might design to fit into my course. How do I go about developing exercises that have a conceptual focus and are productive for my students? How do I know if the exercises I develop are useful for the students?