http://swamij.com/swami-rama-guru.htm
I started to quote but so much was worth quoting that in the end, I decided to quote only the following, which should get you interested:
In the Himalayas the teacher examines the student and the student examines the teacher. When my master sent me to various teachers he told me, “The teacher who can sit still for a long time is a good teacher because he has practiced something. Listen to him. If the teacher changes his posture many times in five minutes, do not waste your time there.” There are certain signs and symptoms that have been explained by the great scriptures. The scriptures help the student to know who is a good teacher so he does not waste much time. Otherwise, what are we teachers doing?