This United States Department of Defense manual, PSM Product Support Manager Guidebook December 2019, is a tool for Program Managers (PMs), Product Support Managers (PSMs), their support staffs, and others in acquisition and sustainment organizations as they develop and implement product support strategies for new programs, major modifications to legacy programs, or as they re-validate and re-engineer product support strategies for existing fielded systems. This guide is focused on identifying, developing, implementing, incentivizing, and measuring quantifiable best value outcome-based product support solutions that optimize Life-Cycle Cost (LCC) and readiness. It delineates processes for outcome goals of systems, ensures that responsibilities are assigned, provides incentives for attaining these goals, and facilitates the overall life-cycle management of system reliability, availability, supportability, and LCC. It seeks to provide an integrated acquisition and sustainment framework for achieving Warfighter performance requirements throughout a program life-cycle. This DAU guidebook advocates the product support guiding principles.