Taking major life decisions, e.g. what career to follow, is difficult and sometimes emotional. One has to find out what exactly one wants, consider the long-term consequences of the decisions and be empathetic for loved ones affected by the decisions. Decision making also deals with establishing and browsing a vast number of alternatives and weighing options according to one’s preferences. Decision support systems can offer help in this process. However, current systems are built on economic models and less suited for untrained decision makers. Therefore, this dissertation focuses on designing decision support systems from a human-centered perspective empowering people to take decisions. Investigations were two-fold, i.e. focusing on requirements and concrete design guidelines and on the methods for engaging of stakeholders in the design process. Requirements were derived from interdisciplinary literature research and exploratory studies with domain experts and users. These highlighted the crucial preparation phase of decision making and the social factors of the process. Design guidelines for the overall system, and in particular preference construction and value-reflection, were derived through design-based research involving experts and users. A dominant theme was the delicate balance between supporting human ways of thinking and reflecting and giving intelligent guidance created by system designers. This balance can only be achieved through close, iterative interactions with end-users, domain experts and designers throughout the design process supported by skilled facilitators. This thesis marks a shift in DSS research from engineering expert systems taking over decision making to designing human-centered support for people to make their own, informed decisions.