Conceptual models serve as abstractions of user’s perceptions of a system. The choice and detailing of these abstractions are key to model use and understanding for analyst and project stakeholders. In this article we consider guidance for the analyst in his creative job of conceptual modeling. More in particular, we discuss guidance offered by diagramming techniques and simulation tools. Therefore we “unhide” their underlying engineering principles. The notion of such principles is helpful in judging techniques and tools for their conceptual richness and completeness, in educating simulation engineers and as a basis for a more structured approach towards conceptual model engineering.