Although existing research in deepening teacher content knowledge provides evidence of program effectiveness, studies often do not provide information on the specific strategies/activities responsible for the gains. Practitioners steeped in this work can provide insights on what strategies/activities work to deepen teacher content knowledge, and why they believe these strategies are "promising practices." These insights can serve as what Elmore calls "sensible propositions" to guide practitioners' activities as researchers work to develop a more rigorous empirical research base to support these insights.