The primary function of metatheory—including metamethod—is to provide a rich source of concepts out of which theories and methods emerge. […] Theories are about the empirical phenomena in a specific subject area, and methods are the procedures used to generate or capture these phenomena; by contrast, metatheories and metamethods are about the theories and methods themselves. More specifically, a metatheory is a set of rules, principles, or a story (narrative), that both describes and prescribes what is acceptable and unacceptable as theory—the means of conceptual exploration of any scientific domain. A metamethod is also a set of rules, principles, or a story, but this story describes and prescribes the nature of acceptable methods—the means of observational exploration—in a scientific discipline. […]
Source: wiktionary