BEST ANSWER: Prepare for this question by thinking of how you can position yourself as a desired commodity. If you are still working, describe the possibilities at your present firm and why, though you’re greatly appreciated there, you’re looking for something more (challenge, money, responsibility, etc.). Also mention that you’re seriously exploring opportunities with one or two other firms.
If you’re not working, you can talk about other employment possibilities you’re actually exploring. But do this with a light touch, speaking only in general terms. You don’t want to seem manipulative or coy.