Allocating kidneys, apportionment in Congress, pricing the internet, and matching of medical interns to hospitals for residency programs are all examples of situations that we face in our daily life, and that modern economic theory can help us solve in a much more satisfactory way than would have been possible just a few years ago. This project is concerned with finding ``good` solutions to such problems. The author addresses two kinds of issues: normative issues of economic justice (Who should pay, and how much? What is fair?); and strategic issues of incentives (How can we provide self- interested economic agents the incentive to behave in accordance with the good of society?). In this research the point of departure then is to identify desirable properties of decision procedures. For each specific class of problems, the author investigates how restrictive the properties are. Do the rules that are used in practice satisfy these properties? If not, are there rules that do satisfy these properties? Can a complete description of all the rules satisfying the properties be obtained? Among them, are some better than others? This methodology is applied to several classes of problems: allocating scarce resources; scheduling and sequencing problems; problems of timing; and problems of allocation over time. Exploiting the considerable methodological advances of the last few years, the goal of this project is to identify methods of reaching decisions that all economic agents find fair and that provide them with the right incentives to participate.