The chapter argues that effective product development begins with rigorous task clarification: defining required properties and framing conditions early, as errors here are costly and difficult to correct, particularly regarding legality and environmental impact. Development tasks may arise from strategy, regulation, customer orders, or quality and cost initiatives. Task clarification integrates cross-functional inputs by describing physical relations, neighboring systems, and product–environment interactions across creation, use, maintenance, and disposal. Vulnerability analyses over the entire life cycle, alongside benchmarking, support strategic positioning. Life-cycle–structured search matrices (Roth) derive explicit requirements per phase and neighbor system. The chapter formalizes the solution space, emphasizing Pareto-efficient alternatives and modular system thinking. A bespoke-shoes case illustrates knowledge-based, order-driven production reducing overproduction, inventory, and emissions. Requirements management maintains consistency as detail increases, avoiding redundancy and controlling change. Over time, explicit requirements often decline while undocumented ones grow, demonstrating the need for disciplined capture. Customer needs are structured via the Kano model (basic, performance, excitement) and recognized as dynamic. Requirement lists document structure, IDs, clear statements, quantifications, and type (Fixed, Target, or Wish) linking non-negotiables, measurable limits, and differentiators. Tools like DOORS and Jama support traceable, prioritized, and life-cycle-aware requirements connecting market, technology, and sustainability.