When I meet a new student, we learn about one another and gradually work our way to talking business. The big question: "why are you here?"
What do they want to learn? I believe that this should be the foundation of our work together, and that if I'm not qualified in the subject then I should send them to someone who is.
Even more important than that ethical concern, though, is showing my students of all ages that these are THEIR lessons, and they have considerable control. If a student wants to learn Harry Potter, no problem....I'll find the sheet music for a non-beginner and we'll work on it right away, or we'll learn Hedwig's Theme by rote if they're beginners. Want to play rock music? Great...tell me your top people and we'll pick a song together so you can learn the chords and play along with the VEVO YouTube video. Want to learn jazz? Here's your first, super-simple improvisation piece. You like tango? Let's play a tango drum rhythm on my djembe. You want to know how the piano works? Let's open it up and shine a light in there.
This ownership of the process fosters intrinsic motivation, which ultimately means happier students and happier parents. It also takes the first step toward building trust: my earning it. The students don't owe me anything, and it is my job to meet them on their turf and show them some paths they didn't know about. Happy, trusting, motivated students are far more likely to take it on faith from me that a particular skill is really worth mastering at a certain stage of their development, and much more likely to focus for longer periods during lessons.
They don't all get the same material in their lessons, but my core goals remain the same and inform the work we do together: change how they think about practicing and mastering a physical skill, teach them how to reflect on HOW they learn, foster a love of all music, and remove opportunities to experience anxiety and disempowerment. With this in mind, I carefully cultivate the options my students have to choose from: for instance, let's say that all three of the pieces they can choose from are good music, approachable for their level of technical proficiency, and offer useful reinforcement or introduction of skills/concepts specific to the students' needs. There will be no "wrong" choices here, but their personal taste is given a chance to count for something.
Often, students who experience the power of choice in music lessons wind up relaxing about it, and looking for it less and less as they realize that it's always there. They wind up focusing on the work, and usually play more music...not less. They choose to play all of the pieces, in the end. A good goal.