This guide has been developed to assist donor agencies (multilateral and bilateral) and policy advisors in a range of organisations working with and for youth. It will also be useful for government, NGO and civil society partners. This guide aims to increase understanding of the growing importance of, and greater potential for, youth participation in development practice and to explore key issues and approaches. But, it goes beyond the rhetoric of many policy advocacy papers, which simply argue for a focus on youth participation. Rather, this guide provides information on how to actually work with youth at a practical operational level in respect of policy and programming. It does this through the provision of promising practice case studies (and their associated resources), and a number of quality standards that will help organisations to get started. Central to this guide is its focus on working with excluded sub-groups of young people, and the importance of building partnerships between adults and youth in a culturally sensitive manner. This is the foundation for all youth mainstreaming work. The guide draws on and synthesises the experience of a wide range of institutions, donor agencies and practitioners.