Methods for observing software users in the workplace will become increasingly important as the number of people using computers grows and developers improve existing systems. Successful redesigns rely, in part, on complete and accurate evaluations of the existing systems. Based on our evaluation experience, we have derived a set of practical guidelines to be used by designers in preparing for the evaluation, performing the field study, analyzing the data, and reporting the findings. By providing a general framework based on ethnographic research, we hope to reduce the likelihood of some common problems, such as overlooking important information and misinterpreting observations. Examples from our ongoing work with the Maryland Department of Juvenile Services are used to illustrate the proposed guidelines.