Some (but not necessarily all) strategic planning participants will be interviewed by the consultant. There is no preparation required. The consultant will want to understand your role, the challenges you face, and what topics you think will be important at the strategy meeting.
These interviews are usually on the same day, face-to-face in your corporate office and are about 30-60 minutes.
If you are out of the office on the day of his visit, your interview may be conducted over the phone.