Despite the critical role of frontline supervisors, research consistently shows that only about half are perceived as effective by their teams. The supervisor–employee relationship significantly impacts engagement, performance, and retention. Yet, many supervisors step into the role unprepared for its challenges. Much is written about the role of executives at the top of the hierarchy but less is written about the first level of management in the organization, the frontline supervisor. This book fills that gap by providing a science-backed, practical guide tailored to new, experienced, and prospective supervisors. Drawing on decades of expertise and consulting work, John E. Kello presents an evidence-based 'how-to' guide for frontline supervisors, addressing the challenges they face with insights from organizational science. It combines research findings with real-world case studies, interviews with supervisors across industries, and self-assessment tools.