Firstly, I believe that the meaning of education has changed in our age. Before us, education was standard. There were one teacher and lots of students in classrooms and the teacher was not aware of the student's characteristics. On the other hand, today I think the teachers should know their students personally in order to guide them. Thus, a teacher should be a friend of the student.
Secondly, there must be a limit of the friendship between the students and the teacher. Thus, the teacher must be authoritarian. Otherwise, the students will not listen the teacher. The teacher should punish the students if it is needed.
To sum up, I think that the best teacher is the one who balances authority and friendship. As I said before, in the age of knowledge, teachers will lead us to the future and the characteristics of the teacher is a very important factor.