The K-8 Early Implementers Initiative has found that careful planning is critical. With thin planning, unexpected detours or dead ends are likely. However, with solid planning, districts are more likely to achieve their implementation goals and may discover some express lanes for their implementation journey. This evaluation report documents lessons learned by the Early Implementer districts through their development and use of master district plans for the Next Generation Science Standard (NGSS) implementation. Intended for district-level administrators and state education policymakers, this report is the fourth in a series of evaluation releases. The report's main topics are: (1) Benefits of developing an NGSS implementation plan; (2) Processes used to develop plan components, including overcoming challenges; (3) Recommendations for developing plans; and (4) Sample components of districts' NGSS implementation plans.