In undergraduate physics lab courses, microcomputers can provide a powerful increase in measurement capabilities over traditional physics instrumentation. However, the implementation of computerized labs must be carefully designed to prevent the machines from obscuring the physics of the experiment. When appropriately used, the power of the computer can help to illuminate the physics of an experiment rather than merely to automate data collection and analysis. Guidelines are presented, along with several experiments, to show the appropriate use of microcomputers in a teaching environment.