As Steve posted in his reply, make sure you read through their social profiles.
But most important, is to value your mentor's time as if they were your own. If your mentorship program is like most Universities, most mentors either are working professionals or have really tight academic schedules. Hence, if they have taken time out for you, make sure you're there on time and are adequately prepared with the questions you'd like to have answered. It's really easy to go off on a tangent and talk about multiple issues. Hence coming prepared with questions and a general roadmap of what you'd like to do/achieve will definitely help you get off the perfect start.
After the end of every session, make sure you summarize and clarify your objectives until the next session. Be sure to send your mentor a thank you email and summarize the points discussed in the email, so that your mentor has a reference before you meet them the next time.
Apart from that, make sure you learn from regular contact with your mentor. I'm sure you'll have a great experience.