Situational method engineering defends the idea that methodologies should be constructed by assembling pre-existing method fragments from a repository. The structure of the repository, the kinds of fragments that it can store, as well as the possible relationships among them, are dictated by an underlying metamodel. One of the aspects that must be studied is that of the granularity of the individual method fragments in the context of the metamodel to which the fragments are conformant. This becomes especially relevant in a service-oriented method engineering context, where interoperability and composability of fragments from multiple repositories is a key issue. This paper applies some theoretical works on granularity to the study of both the granularity and the size of method fragments, recommending some best practices that should be adopted in order that the resultant method fragments are atomic and therefore likely to be consistent in quality thus leading to higher quality constructed methodologies and paving the way for easier composition and interoperation of fragments.