Great leaders ask questions. But not just any old question, great leaders ask thoughtful questions that require thoughtful answers. Usually this means staying away from yes/no answers. A great leader knows how to ask questions which will illicit the most honest response. That's an interesting idea. Here's what I mean:
Great leaders know when a question is difficult and phrases it in the way which encourages honesty by giving the person answering the easiest way to say the hard things (the thing they worry most won't be the "right" answer).
Great leaders are also quick to understand how questions can empower others to take ownership and responsibility.
Great leaders recognize there's no weakness in asking questions and understands that asking questions is a way to lead others to finding a similar solution (or exploring alternative thinking to their own).