Identifies critical components that enable a youth mentoring program to flourish and without which mentoring efforts are at risk of failure. Laying a solid foundation is essential not only for the long-term success of a mentoring program, but also for the safety and well-being of the youth being served. This guidebook offers program administrators, board members, onsite program coordinators, and staff information on the 5 elements of programmatic success: (1) strong agency capacity, including a written mission statement and program development plan, strong knowledge of mentoring and youth development research, written policies and procedures manual, access to training and technical assistance services, and community awareness of the program; (2) proven program design, including a written recruitment plan with multiple strategies, appropriate mentor screening procedures, pre-match training for all new mentees and mentors, and established procedures for monitoring matches; (3) effective community partnerships, including collaboration with other local youth service organizations; (4) sustainable resource development, including a resource development committee and written development plan; and (5) useful program evaluation, including use of data for program enhancement. Program administrators and others can use the components recommended in the guidebook to either help structure the development of new programs or audit existing programs.