In this paper we present a participatory design method for the conceptual design of the user interface, which uses different techniques for capturing the mental models of experts and users. Each technique is carefully specified, and it is implemented in the user interface design for an interactive system in the educational context. The implementation of these techniques allowed the definition of the domain model, first interface sketches, specification of technological components, scenarios, among others. Likewise, their implementation evidenced the need of introducing a brand-new technique that complements the method.