Good mentors are hard to find. A good mentor is one who can devote his/her time to hone your skills, help your personal and professional growth and provides guidance selflessly.
Treasure him if you are able to find one. Your mentors are devoting their precious time, experience and efforts for your growth. Engage with them with an attitude of extreme gratitude and try to offer help/support in whatever manner you can.
Building a good relationship is key for you to get the best from your mentor.