Contextual interviews

Contextual interviews are conducted in the same environment or context where the service is realized. This ethnographic technique allows for the interviewer to observe and interpret the behavioral pattern that is of interest.

Additional reading
Holtzblatt, Wendell, and Wood.
Rapid contextual design: a how-to guide to key techniques for user-centered design
Elsevier, 2004.

Cooper, Reimann, and Cronin.
About face 3: the essentials of interaction design
John Wiley & Sons, 2007.