This guidebook summarizes learning on the role of intermediaries and how to build organizations that perform intermediary functions effectively and efficiently. An introduction defines intermediaries, in the context of youth-serving systems, as staffed organizations that connect schools and other youth-preparation organizations with workplaces and other community resources so young people can combine learning with doing and become better prepared for postsecondary learning and careers. Part I details the strategic and operational functions of intermediaries. With 14 real-world examples, this part demonstrates the diversity of experimentation across the nation, while highlighting common features of effective intermediary entities and activities. Part II elaborates on a five-stage model that describes the process of connecting schools and youth-serving organizations with workplaces and community resources. Part III outlines issues that organizations involved in the School-to-Work Intermediary Project have identified as critical to sustaining intermediaries linking schools and workplaces. Part IV explains how to use a set of design and implementation tools developed by the project to assist local youth-serving efforts. The appendix provides details on the project, including a summary of its activities, information on contacting members of the Intermediary Network, and the directory to a companion CD-ROM available separately. (YLB)