Drawn from the experiences of the Cornell Youth and Work Program, a 4-year demonstration project that adapted elements of European L4 apprenticeship in the United States anc emphasized opportu-:!.ties for youth to learn at work, this guide is written for people in workplaces and schools who plan, direct, or evaluate work-based learning opportunities for youth. Following an introduction that describes the demonstration projects, types of work-based learning, and the principles derived from the project, the guide contains seven sections. The sections cover the following topics: (1) technical competence (getting started, designing a multiyear program); (2) breadth (why teach all aspects of the industry, why rotate, why support projects and complex activities, what makes a good project); (3) personal and social competence; (4) expectations and feedback; (5) teaching roles (coordinating, managing, coaching, mentoring in work-based learning programs); (6) academic achievement; and (7) career paths after high school. A concluding section suggests next steps for restructuring schools and workplaces, forming partnerships, and building a school-to-work system. An appendix contains statistics and samples from the demonstration project. (KC) Reproductions supplied by EDRS are the best that can be made from the original document.