This book provides school principals and those responsible for pedagogical supervision the necessary tools for their professional development, whether in formal (continuing education) or informal (self-taught) contexts. It presents for each knowledge, know-how, know-how and know-how to become two sections. The first, titled What the supervisors say, presents testimonials from a research-action-training project (Ministry of Education and Higher Education of Quebec, 2014-2017) which brought together 37 principals of two school boards in professional learning communities (PLCs) to discuss their pedagogical supervision practices in their school. This second section proposes self-assessments grids. The book is also punctuated with practical exercises and reflections to develop the targeted skills in supervision. This book is an essential reference for all supervisors. It presents experiences in teaching, research and training. It is a functional and practical guide to acquiring and consolidating pedagogical supervision skills.