Frequent five-minute visits focused on specific "look-fors" can give principals valuable information about what's working--or not working--in their schools. A program of brief but frequent classroom walkthroughs has become an increasingly popular strategy in recent years for informally supervising teachers and observing classroom activities. But what is it about walkthroughs that can help improve instruction? Are there elements of the process that should receive special attention in order to maximize their effectiveness? This article discusses several elements that are critical to the success of a walkthrough and lists some positive outcomes affecting instruction. It ends with some recommended steps for principals planning for classroom walkthroughs. (Contains 3 online resources.)