Games used by organizations generate a wealth of valuable output in terms of knowledge. In order to maintain the produced knowledge, such as the explicit, e.g., logging and questionnaires, and implicit/tacit knowledge, e.g., experience from game sessions, a knowledge management system (KMS) should be employed. This paper starts by giving a brief description of the building blocks for a KMS and then proposes a methodology that combines three different methods, namely, semi-structured interviews, causal maps, and the Q-methodology, to illustrate how tacit knowledge from principal stakeholders (game designers and project team members) can be extracted as part of building a KMS. The proposed methodology is applied in a case study related to the railway sector.