Diagnostic abilities required during the on-going process of teaching include perception, interpretation and decision-making skills. They are regarded as important prerequisites for adaptive teaching. To teach these skills, several teacher education programs have been developed. However, a theoretical foundation is still missing. Here, we introduce a model for learning these diagnostic skills. With this model, we derive guiding principles for designing a framework using video analysis in teacher education programs. We show that some implications of this model have already been integrated in current programs. However, we also present new aspects. In particular, reflection on unexpected events might be a good way to enhance teacher education programs.