Field Studies Done Right: Fast and Observational by Jakob Nielsen

All the talk about “anthropology” obscures the fact that all development teams should do field studies, and that teams can run studies on their own, without hiring a bunch of PhDs.
Summary: Field studies should emphasize the observation of real user behavior. Simple field studies are fast and easy to conduct, and do not require a posse of anthropologists: All members of a design team should go on customer visits.