Helping to build what are often referred to as "social-emotional" or "21st century skills" is an important contribution that many youth programs make and more could be making. Yet these efforts remain underrepresented in the program evaluation literature, in part because they cannot be measured using administrative records or other databases to which schools and programs might have access. Practitioners and funders regularly ask us for advice about how to measure these skills. In response, we developed this guide, which summarizes information about tools that programs can use to measure youth progress in these areas. The guide builds on and complements several related resources available. (author abstract)