For a new piano teacher having a good, qualified teacher makes a huge difference in how well they will be able to teach. I have learned so much from my current teacher. For a piano student, having a teacher who is constantly learning and working to improve herself (or himself ) makes a great difference in how well they will be able to play piano.
I really hope that my present students are benefiting from their lessons more than my first student. Honestly, I still worry that I am not a very good teacher. But the difference between then and now is that I am being taught how to teach.
Ways to better yourself as a piano teacher:
-find the best music teacher in your area
-attend other people's music lessons (especially beginner lessons)
-read a lot (books, magazine and website articles, blogs)
-research a lot