Your journey as a mentor is a personal one but here are some general tips and suggestions :
Time and commitment
It's pretty obvious that you need this. But don't forget to communicate. Let your mentee know if you would be busy, or inform the coordinators. Of course, sometimes you might not be sure just how busy you would be, but try to let the coordinators know that you just might be away so that plans could be made.
Make a personal connection and listen
Mentoring isn't about you telling your mentee what to do : you're only helping them realize what they can do. In the process, you get to make a new friend, IC and perhaps even OOC. Some mentees might have specific questions or concerns so do try to find out what matters more to him / her (and the writer). Then, it might also be nice to share your own experiences.
Ask specific questions
Asking "Do you have any questions ?" will most likely get you a "No" or "Not yet". It might be more useful to ask, for example, "Do you know how to enrol in classes ?" or "Do you know the Beauxbâtons requirements to move to Year 2 ?" When your mentee seems unable to explain problems, going in chronological might be useful, eg. "How did this first start ?", "Could you tell me what you first tried ?"