I began teaching at age 14 after I had completed grade 6 with the Royal Conservatory of Music. This was such a new experience for me! My own teacher invited me to her studio with my student so that she could observe me teach, but I was so nervous I froze up! My teacher ended up teaching my student and I ended up watching.
Having been on the teaching side and the student side of lessons recently, I feel like I have a decent grasp of what music lessons should be about. (I am taking guitar lessons this year, for the first time!) Students are usually very excited to start lessons, and many will put in the practise time at first, but a lot of students lose their drive after a month or two. The student is often not progressing as fast as he or she would like, and the lessons aren't always exactly what the student was expecting. This is a common issue with students, and it is one I strive to avoid.
Before I start lessons with my students, I need to know what their musical interests and background are. I find out what kind of music they listen to, what kind of role models they have, what kind of things they can already do. I especially need to know what kinds of things the student wants to learn to play! A lot of teachers are classically trained and intend to classically train their students. I am classically trained, but the only way I will point my student in that direction is if he or she wants to go there!