Ask Good Questions!
Effective, active listening is an integral part of any effective mentoring relationship. But listening is just one part of the mentoring conversation, asking good questions can be just as important. Mentors should be sure to ask plenty of broad, open-ended questions that will elicit good responses. If applicable, follow up these questions with a "how?" or a "why?" to help uncover the reasoning behind a protégés ideas. Be sure to follow up questions with careful, active listening.
Know Your Limits
Mentoring is hard work for both the mentor and mentee. However, it's important to not overwork yourself in a mentoring relationship. Set boundaries early on (e.g. how often you will meet, how much work is to be expected), and if you find yourself getting worn out, let your mentoring partner know. The point of a mentoring relationship is to foster learning, not exhaustion!
Go into your mentoring conversation with an idea of what you want to talk about. The mentor and the protégé should both prepare beforehand with questions and points that they want addressed.