a. Initial Sample (based on diversity): structuring the list of high-frequency users in frequency order, and then selecting the informants such that they spanned as broad a range of attributes as possible.

b. Subsequent Samples (based on informal hypothesis and developing a theory): should abductively test the initial hypothesis.

c. Theoretical Sampling: provide the strongest test against the developing theory (abduction), to reveal its weaknesses early, and to broaden the range of situations and attributes over which the theory makes good predictions or descriptions.