This chapter reviews basic considerations in the development of tools to assist a decision-maker in making informed decisions and improve decision outcomes. This chapter reviews software engineering guidelines that facilitate the development of easily maintainable software tools. Water in the farm and the basic principles involving transfer of water in the farm are reviewed with a special focus on irrigation scheduling. Examples of successful decision aids since the appearance of the personal computer are presented that illustrate the evolution of decision support systems and its close association to information technology developments. Potential outcomes of fourth industrial revolution technologies are briefly discussed, including the beginning of a complex system approach to decision-making aids.