Humans are not omniscient. They do not come equipped with the ability to run computationally demanding calculations quickly in the mind. Rather, we make decisions under the constraints of limited information processing capacity, knowledge, and time—be they about the likely performance of stocks; which movie to watch in the cinema; whom to court in a speed-dating session, or whether to admit to the hospital a patient who has registered at the emergency room reception. According to the fast and frugal heuristics research program, humans can nevertheless make such decisions successfully because they can rely on a repertoire of simple decision strategies, or heuristics. These simple rules of thumb can perform well even under the constraints of limited knowledge, time, and information-processing capacity because they exploit the structure of information in the environment in which a decision maker acts and build on the ways evolved cognitive capacities work, such as the human memory system. Together, these simple rules of thumb form an adaptive toolbox of the cognitive system, where the tools are heuristics a decision maker uses to respond adaptively to different decision situations, each one appropriate for a given task. However, even though it is an important assumption of the fast and frugal heuristic approach that decision makers respond to different decision situations by selecting the heuristic that is appropriate for the task, relatively little is known about how such a choice is made. The goal of my dissertation is to contribute to our understanding of the corresponding mechanisms of heuristic choice—or, to use a more general term, strategy selection. Specifically, my dissertation focuses on the selection of decision strategies for making inferences about unknown quantities and uncertain events in situations in which all available information must be retrieved from memory. In doing so, I investigate how the interplay between the human memory system, the environment in which decision makers act, and available decision strategies can lead to the emergence of adaptive mechanisms of heuristic selection.