Encourage your candidate to ask ‘open questions’: questions that cannot be answered with ‘yes’ or ‘no’ (and often begin with ‘who’, ‘what’, ‘where’, ‘which’, or ‘how’).
Advice your candidate to always listen carefully to others.
Encourage your candidate to invest time and attention in another person and to express this interest physically e.g. by shaking hands, looking the other person in the eye, sitting upright.
Explain the importance of knowing the customer’s interests and, possibly, hidden agenda.
Ask your candidate to take careful notice of another person’s verbal signals and body language while talking to him. Explain that the two may diverge - which can be to his advantage.