The structural and social features of a girl’s community play a critical role in determining what effects programs for adolescent girls can achieve. Girls’ communities include both the physical spaces girls must navigate and adults and peers who shape their beliefs about marriage, work, and education. This action guide focuses on key questions to ask when designing programs: How many girls live in a given community? Is the community urban, peri-urban, or rural? Is it formal or informal? How stable or cohesive is a community? Who is considered a “community member”? What resources exist for girls in the community, and who has access to them? How do economic and social pressures shape community norms about marriage, education, work, and gender roles? The action guide offers tips on how to find answers and provides real-world examples that demonstrate how to use community-level insights for action for adolescent girls. It was written for people who design, manage, and assess community-based programming.