Many districts are using content-focused coaching as a strategy to provide job-embedded support to teachers. However, the current coaching literature provides little guidance on what coaches need to know and be able to do to engage teachers in activities that will support their development of ambitious instructional practices. Furthermore, little is known about how and why effective coaches choose to design particular types of activities with certain teachers. In this article, we report an exploratory case study that examined a mathematics coach who consistently engaged teachers in coaching activities that had the potential to support their development when she worked with them one-on-one in their classrooms. In presenting an analysis of the coach's design of coaching activities, we describe five aspects of her planning practice and delineate the knowledge implicated in those practices. The findings clarify goals for coaches' professional learning, and therefore have implications for school and district coaching policies.