As district leaders search for the best ways to improve student learning with the Common Core State Standards, California districts are leading the way as early implementers of the new standards. The ideas and lessons emerging from their work can help other educators maximize the effectiveness of their own implementation efforts. This brief describes Sacramento City Unified School District's approach to developing units of study that guide teachers' classroom practice. The units provide a valuable tool for designing curriculum and instructional materials, but just as importantly, they have driven teacher capacity building and engagement in the implementation of the new standards. This brief examines the units of study strategy as it has unfolded in Sacramento, identifies some of the key points of evolution since the district began its work three years ago, and discusses some of the challenges and tensions facing districts that might employ a similar approach. Key findings in this brief include: (1) Achieving the appropriate level of specificity--Teachers must consider many specific elements of classroom instruction when implementing a unit of study; (2) Balancing teacher empowerment with quality control--Developing units of study can help teachers understand the standards in deeper and more meaningful ways than traditional approaches, but the model also calls on teachers to act as curriculum developers; (3) Leveraging teachers' experiences and perspectives--The units of study fundamentally rely on teachers' professional judgment to drive Common Core implementation efforts; (4) Building trust to facilitate teacher growth--For these efforts to be successful, district and site leaders need to create trusting environments where teachers feel comfortable taking risks; and (5) Providing enough time and support--Finding time for teachers to learn and engage in the unit development process is an ongoing struggle. [Contains notes. The development of this brief was also supported through contributions from the California Education Policy Fund, and the Silver Giving Foundation.]