How are doctors trained in the art of diagnosis?

I am not a doctor myself, but I work for a medical technology company that has developed Videolab, a software to make safe patient recordings for communication training, which is an important part of the diagnosis of medical students. So I can't speak to all parts of the diagnosis but as far as communication is concerned, the way it works in most German universities is that the students come to an actor who is prepared to act out a certain disease and depending on how advanced the university is either with video recordings or just verbally get feedback in different ways such as self-reflection, peer feedback and are then evaluated after an Objective Structured clinical examination according to certain pre-defined criteria.

Hope this helps :)