The author describes techniques that he uses to interactively teach economics principles. He describes an experiment on market entry and gives examples of applications of classroom clickers. Clicker applications include (a) collecting data about student preferences that can be used to construct demand curves and supply curves, (b) checking students' knowledge of central concepts, and (c) playing interactive games that illustrate economic concepts. (Contains 11 figures, 2 tables, and 7 notes.)