I played violin for a few years, but I also had private piano lessons for many years and am much better at piano than violin. Anyway, I don't think there's any one universal trait that makes someone a good teacher (other than knowing how to play well, obviously). Otherwise, it's a matter of finding an instructor who has a personality that you can mesh with and a style of teaching that is good for you as an individual. Some teachers are very focused on technique, making sure every note is played exactly the way it is written in the music and that the fingering, etc is correct; other teachers are more into the artistry of music and tend to be more liberal with the technique. If you're looking for a teacher, I would interview a few, describing your (or your child's) learning style in other areas if you don't have musical experience, and see what his or her approach would be to teach you. You can always change teachers if needed.
at 4:02 PM on Jun. 24, 2010