Students are more and more incited to carry out work placements in firms during their training. However, the lack of intellectual instruments adapted to this kind of exercise raises a problem. Left to their own devices or overburdened with ill-suited precepts and methodologies, the students do not take full advantage of their work experience. By relying on my research experiences in firms, on the tradition of field studies in sociology and on teaching experiments carried out in several schools of engineering and management, I propose a practical, explicit and debatable method of direct study of the processes of the work situation.