Scarcity is the defining characteristic of water in the western United States. Freshwater is naturally limited to precipitation, runoff and aquifer storage. Climate variability and extreme weather events -- especially drought -- increase uncertainty across timescales, from days to decades. And yet demands for water continue to grow, along with the population and economy of the West. As cities, industry, energy developers and other users seek new secure water supplies, they increasingly turn to voluntary water transfers. Water transfers are occurring throughout the West, and they will become increasingly important as new demands stress limited supplies. The goal of this report is to suggest ways to make water transfers more efficient and equitable, while not promoting or opposing individual transfer proposals. This report examines water transfer practices across the western states, highlighting successful models, analyzing case studies, and identifying leading practices. The goal is to share lessons and tools and to identify specific steps that states can consider in order to improve water transfer outcomes.