Your goals and your students' goals won't always be the same. Sometimes your really talented students won't feel the need to pursue music as a career.
Sometimes students stop taking lessons for reasons that have nothing to do with you. You never know what's going on in a student's life outside of the studio.
Establishing a routine and a framework for the lesson makes your students feel more comfortable taking musical risks in their playing. Stability in the studio makes students more willing to play in the sandbox and try new techniques.
Have at least three ways to describe any given concept. Not everyone will need something explained the same way you would need it to be explained to you. If your student doesn't understand something the first time you explain it, it's not their fault. Keep digging until you find a way to communicate with them.
Keep learning new things if you want to be a great teacher. Learning a new skill, whether it's musical or not, brings you back to the "beginner's mind."
What have your students taught you? Share in the comments!