The purpose of this guide is to help college administrators and staff members implement the following two interventions designed to increase summer enrollment rates at their schools: (1) An informational campaign of personalized student communications using email and mail and informed by behavioral science. The campaign simplifies academic, financial aid, and procedural information related to summer enrollment, reminds students about that information, and motivates them to follow through and register for courses; and (2) A similar informational campaign paired with a "last-dollar" tuition-assistance grant that covers the difference between each student's summer tuition and fees and any grant financial aid (such as Pell Grant funding) they have available for summer courses. The interventions were developed and evaluated by MDRC in partnership with the Ohio Association of Community Colleges and 10 Ohio community colleges, as part of the Encouraging Additional Summer Enrollment (EASE) project. These interventions proved effective in MDRC's 2017/2018 randomized controlled trials--the most rigorous form of evaluation--increasing both enrollment in summer courses and credit attainment. Although they did not increase enrollment in the subsequent fall semester, the additional credits earned during the summer helped students make progress toward earning a degree. A resource toolkit includes: (1) Message templates for each strategy, annotated with instructions and tips. Plus an editable version that you can download, copy, and customize; and (2) A summer Pell Grant calculator to estimate students' Pell Grant awards and create personalized messages to tell them how much funding they may have available. [This report was written with Dan Handy.]