The anthropologist must study the whole of the social life. It is impossible to understand clearly and comprehensively any part of a people's social life except in the full context of their social life as a whole. Though he may not publish every detail he has recorded, you will find in a good anthropologist's notebooks a detailed description of even the most commonplace activities, for example, how a cow is milked or how meat is cooked. Also, though he may decide to write a book on a people's law, on their religion, or on their economics, describing one aspect of their life and neglecting the rest, he does so always against the background of their entire social activities and in terms of their whole social structure.
Such, very briefly and roughly, are the essential conditions of good anthropological fieldwork.
Evans-Pritchard, E. E. 1951. Social Anthropology. London: Cohen & West. pp. 77-80.