Designing an Effective User Study
http://www.stc.org/confproceed/1998/PDFs/00046.PDF

Hammar, Molly and Dawn Stevens
STC Proceedings
1998

Abstract:

When it comes to learning about your users, a plethora of methods await you. But which one is best for your situation? The answer depends on many factors, including the kind of information you hope to discover, the time and budget you have available, and your access to users.