Problem formulation is one of the most crucial steps in any systems engineering effort. This paper describes a five-step approach to systems problem formulation in which the different crucial aspects are addressed consecutively. The approach first emphasizes (1) the analysis of a problem's context and (2) the formulation of objectives, as this may significantly affect the system boundary and the spectrum of alternatives taken into account. Next, (3) an actor and dependency analysis and (4) an uncertainty analysis follow, which contribute to (5) adjustments to the system boundary and enrichment of the criteria and alternatives to be considered. The essence of each step and the use of simple, conceptual methods is illustrated using an example.