Encourage your candidate to ask others for 360º feedback regarding the way he expresses his vision. What is their impression, what goes well and what could be improved? Discuss the results with the candidate.
Engage your candidate in a fantasy about the future. Set no restrictions; everything can be thought and said, no matter how strange.
Ask your candidate to define a number of big problems at work and to think about causes and possible solutions. It is important those solutions are realistic and attainable.
Ask your candidate in what direction the organization or department should go in order to overcome future problems. How could he contribute? Discuss potential obstructing thoughts the candidate might mention.