Shadowing belongs to the participant observation. Prime principle is to influence the observed person as little as possible in order to keep the behavior natural. Questions to the observer are only allowed in critical or unintelligible situations.
The person is observed in the natural context over a longer period (minimum one day). With that context and informal information, specific views, actions and procedures. The knowledge acquisition is correspondingly high. The shadowing needs little preparation it however is time consuming. A subsequent structured evaluation process has been proven successful.
The results are statements regarding requirements, actions and real goals of the target group as well as high identification possibilities of optimization potential and problems in context.