Research shows low-income students suffer disproportionate learning loss over the summer and because those losses accumulate over time, they contribute substantially to the achievement gap between low- and higher-income children. The Wallace Foundation is funding a five-year demonstration project to examine whether summer learning programs can reduce summer learning loss and promote achievement gains. This report, the first in a series, draws on emerging lessons from six school districts in the study -- Boston, Cincinnati, Dallas, Duval County (Florida), Pittsburgh, and Rochester (New York) -- that offer full-day programs for five to six weeks free of charge to large numbers of elementary students. The report synthesizes the key lessons learned about how to establish and sustain effective programs. The most emphatic recommendation is to start planning early, no later than January, and include both district and summer site leaders in the process. Many problems identified by the researchers -- from weak teacher training to ineffective transportation -- could be traced to a rushed planning process. Other guidance includes adopting a commercially available curriculum, establishing enrollment deadlines, ensuring sufficient time on academics, and selecting enrichment providers with qualified staff experienced in behavior management. To manage costs, the authors suggest designing the program with costs in mind -- by hiring staff based on projected daily attendance rather than number of enrollees, for example, and by restricting the number of sites to control administrative costs. [For the summary to the report "Getting to Work on Summer Learning: Recommended Practices for Success, 1st Ed. Summary. RAND Summer Learning Series," see ED594504. For the appendix materials "Getting to Work on Summer Learning: Recommended Practices for Success, 1st Ed. Appendix Materials. RAND Summer Learning Series," see ED594506. For the second edition of the report "Getting to Work on Summer Learning: Recommended Practices for Success, 2nd Ed. RAND Summer Learning Series," see ED591732.]