This book offers a toolkit of field-tested strategies to help teacher leaders maximize their effectiveness. The teacher leaders who get the best results are the ones who explore the role's full potential, but it can be a challenge to get beyond a basic understanding of the responsibilities involved. The National Institute for Excellence in Teaching (NIET) wants to make it easier. This volume presents best practices and tools that teacher leaders can use to unlock their own power and drive lasting instructional improvement across schools and districts. Current and future teacher leaders will learn how to examine their context as instructional experts; understand their approach to leadership and how to work with other leaders in their school; develop expertise in evidence-based instructional practice; support the implementation of high-quality curriculum; build effective learning environments and support colleagues' efforts to do the same; understand how to use data and assessment to support student learning and inform instructional practice; acquire coaching skills to help build colleagues' capacity; lead effective collaboration and scale teacher effectiveness; and use their voice to influence decisions that affect students and fellow teachers. Along with guidance on these practices and skills, readers will get the perspectives of teacher leaders engaged in this work and acquire dozens of NIET-developed tools they can use to unleash the power of effective teacher leadership in their own school and district. This book is a co-publication of ASCD and the National Institute for Excellence in Teaching.