Designing and implementing effective provision of extension is complex, and efforts to strengthen extension services often fall into a trap of adopting “best practice” blueprint approaches that are not well-tailored to local conditions. An expansive literature examines the promises and pitfalls of common approaches, including training-and-visit extension systems, farmer field schools, and many others (Anderson and Feder 2004; Anderson et al. 2006; Waddington and White 2014; Scoones and Thompson 2009). To understand extension systems and build evidence for what works and where, the “best-fit” framework, a widely recognized approach developed by Birner and colleagues (2009) and adapted by Davis and Spielman (2017), offers a simple impact chain approach (Figure 1). The framework focuses on a defined set of extension service characteristics that affect performance: governance structures and funding; organizational and management capacities and cultures; methods; and community engagement — all of which are subject to external factors such as the policy environment, agroecological conditions, and farming-system heterogeneity. To enhance extension performance and, ultimately, a wide range of outcomes and impacts, new and innovative interventions can be applied and adapted within this set of extension characteristics.