This comprehensive guide outlines how to conduct participatory assessments with youth and community members for improved youth reproductive health and HIV prevention. Drawing on the experiences of YouthNet (a five-year global program to improve reproductive health and prevent the spread of HIV/AIDS among people 10 to 24 years old) in Namibia, Tanzania, and Ethiopia, it reviews youth participation, guidelines for training community participants, and suggestions for adapting the methods and tools for use at other projects.