Consider a certain issue or problem with your candidate by brainstorming. Do not put his suggestions up for discussion (yet). Review the pros and cons of each suggestion together.
Ensure your candidate talks to people who have insight in upcoming trends and influences, and discuss this experience.
Provide your candidate with a safe environment. Encourage him to experiment and play with new ideas and concepts. Set no boundaries.
Encourage your candidate to work with a colleague who is known to be innovative. This may inspire him to new, innovative ideas.
Engage in an associative or brainstorming session with the person over a certain topic or a problem that is bothering him. Use development and brainstorming suggestions, and possibly mindmapping techniques.