Given the current interest in organizing teacher education around core instructional practices that help preservice teachers enact ambitious aspects of teaching like leading classroom discussions, this article investigates an example from the experience of a preservice teacher as she works on orienting students to each other's ideas. Resulting problems of practice are examined, along with the factors that contribute to their emergence in real time. The study also brings attention to the complexity of this work and the ways in which novice teachers' knowledge, development as learners, and available resources in the contexts of their work contribute to how they approach and manage these problems.