Classroom observation has changed dramatically in recent years. Trivial checklists have given way to research-based rubrics that describe important aspects of teaching and, for each aspect, explain the difference between more and less effective practice. Instead of asking if the lesson objective was posted, these new instruments typically ask to what extent the objective was clear to students, how well the teacher connected the objective to students' prior knowledge, and to what extent the teacher reinforced the objective throughout the lesson. This clarity around what to look for in a lesson has tremendous potential. It makes it possible for different observers to reach the same conclusions about how well a lesson demonstrates a set of practices that matter to student learning. This is essential for trust and aids decision-making. District leaders also need observers to produce trustworthy data to inform their systemwide investments in professional development. Perhaps less widely understood is that the same agreement about the indicators of effective teaching also enables observers to give more effective feedback. Fortunately, researchers and leading school systems have identified what observers need to know and be able to do--and the kinds of activities that can be used to develop, monitor, and reinforce those skills. This article discusses six skills every observer needs and how to build them: (1) Know the rubric; (2) Collect evidence; (3) Understand bias; (4) Recognize and sort evidence; (5) Use criteria for rating; and (6) Coach teachers.