This guide is based on findings of a year-long study undertaken by the Institute of Museum and Library Services (IMLS) to evaluate Institute-sponsored programs for youth aged 9-19 between 1998 and 2003, and discussion with the IMLS Youth Action Committee and practitioners about the kind of information needed for planning and implementing effective youth programs. It includes resources and references to works that have been gathered from the fields of youth and community development, education, and informal learning. The guide is presented in two sections: (1) What Works for Youth in Museums and Libraries; and (2) Resources for Practitioners. The guide is particularly targeted to museum and library practitioners who are building, or wish to build, strong programs to reach and engage youth. It is also intended for community planners, youth development leaders, and educators who want to build bridges across the many types of organizations and institutions that serve youth in American communities. (Contains 1 figure and 20 resources.)