4-H volunteers and staff are often faced with providing educational programs and opportunities for youth with wide ranges of age and ability. To address this challenge, researchers from the University of California Cooperative Extension developed and tested a Best Practices Matrix that outlines domain-specific, age-appropriate characteristics of youth and their applications to 4-H programming. Post-implementation surveys that included six forced-response and five open-ended questions were collected from 48 adult volunteers who attended volunteer development workshops. Outcomes indicated that participants improved their understanding of youths' developmental characteristics and how to use the matrix to help improve their project and activities. (Contains 1 figure.)