In brief: Observing the reactions of your conversational partner during the conversation.
Ordinarily people tend to ask questions with a certain goal or purpose in mind. They then listen to the answer as if the answer is based on the question as they meant it to be. Yet the other is answering based on what they understood the question to be. Observational listening trains the listener to let go of their own goals and interpretations and concentrate on the reactions evoked. In other words, the listener tries to find out what the question meant to the other. In this way he or she “gets it” and is able to bring depth into the conversation in a natural way, without resorting to tricks.
Observational listening is grounded in empowerment, empathy and a genuine facilitating attitude.