Application development and delivery (AD&D) leaders use custom software development service providers to achieve faster time-to-market, increase business agility, and get hard-to-find help creating innovative solutions. We interviewed 22 clients of development service providers for “The Forrester Wave™: Midsize Agile Software Development Service Providers, Q2 2019.” This report summarizes what we learned from these practitioners about how to get the best from software development partners.