Operations research (OR) generally centers on building a mathematical model of an operational system. In contrast, the branch of OR called decision analysis (DA) centers on building a mathematical model of the preference structure of a decision maker. The goal of DA is to reveal to him or her what decision should be made by eliciting details about what he or she wants to accomplish in a complex situation, perhaps one with many uncertainties and many competing priorities. The purpose of this chapter is to outline how DA fits into military operations research as a whole, and then to present some standard best practices that will cover multiattribute decisions, one of the most common types of military and defense problems that calls for DA.