More than three decades after their introduction, diagnostic classification models (DCM) do not seem to have been implemented in educational systems for the purposes they were devised. Most DCM research is either methodological for model development and refinement or retrofitting to existing nondiagnostic tests and, in the latter case, basically for model demonstration or constructs identification. DCMs have rarely been used to develop diagnostic assessment right from the start with the purpose of identifying individuals' strengths and weaknesses (referred to as "true" applications in this study). In this article, we give an introduction to DCMs and their latest developments along with guidelines on how to proceed to employ DCMs to develop a diagnostic test or retrofit to a nondiagnostic assessment. Finally, we enumerate the reasons why we believe DCMs have not become fully operational in educational systems and suggest some advice to make their advent smooth and quick.