During the past five years, the authors have collaborated to provide elementary school teachers with professional development that focuses on both mathematical content and pedagogy. All the professional development was created in keeping with the best practices. Many conversations evolved around the role of a coach and the most effective ways to help support teachers in their work with elementary school mathematics learners. The authors learned that the most effective professional development happens in the context of one's own classroom--but not usually by oneself. They observed that although professional development can be an individual endeavor, it is easiest and most sustainable with a colleague or a community of colleagues. Elementary school teachers generously opened their classrooms to the authors, who learned multiple lessons about the attitudes and opportunities that help to cultivate successful, ongoing professional development. Here they describe the lessons and offer suggestions for tailoring professional development to one's own specific needs. (Contains 1 table.)