Some pre-service teaching activities can contribute much to the learning of pedagogical content knowledge (PCK) and subsequent teaching as these activities are "generating" PCK within the pre-service teacher's own classroom. Three examples are described: preparing exhibitions of science experiments, assessing preconceptions, and teaching using embedded formative assessment in which assessment "leads" teaching and almost inevitably results in the development of PCK. Evidence for the effectiveness of the methods is based on the author's experience in teacher education programmes in different countries, but will need to be confirmed by research.