Knowledge level modelling of knowledge-based systems is commonly facilitated with a library of generic models, that are specialized for classes of applications. The paper discusses guidelines for adapting such generic models, in particular task decompositions, to a given application. In this field of adaptation of reused knowledge structures, the kind of case for which reuse and adaptation is made is very complex and open - the development of a knowledge-based system. In the current state-of-the-art, the process cannot be automated, but must be controlled by a human knowledge engineer. Therefore, the results so far are informal guidelines.