Modeling and modeling methods are crucial for information systems engineering but are seldom seamlessly integrated into all phases of development and operation: Practitioners challenge the benefits of modeling and complain about the confusing variety of concepts with overlapping semantics, symbols and syntactic rules of today’s standardized, “universal” modeling languages. Therefore, domain-specific modeling languages (DSMLs) are gaining increasing popularity: they are lean and convenient, support the productivity of modeling, and help to increase model quality and comprehensibility. There are, however, few approaches to embedding a DSML into a domain-specific modeling method (DSMM) that provides guidelines about how to use a given DSML and to evaluate related models. This chapter aims to make a contribution towards filling that gap by discussing, as an example and proof of concept, a domain-specific modeling method for the human cognitive modeling language HCM-L, a DSML for the domain of active and assisted living. As a modeling language without tool support has no chance to be used in practice, we are conducting that discussion on the basis of HCM-L modeler, a tool that was implemented using the metamodeling platform ADOxx and can be accessed via OMiLAB, the Open Models Laboratory for modeling method engineering. HCM-L modeler is component of an ambient assistance system for supporting elder persons in mastering their daily life activities.