Check out this excellent article by Elissa Milne. Click Here to read it.
I would also add to this list:
11. Make sure your child knows the difference between high/low and loud/soft. You wouldn’t believe the number of students who will say “the music got higher” when what they mean is that it got louder. High/low refers to pitch, NOT volume. (I blame the advent of technology that allows us to turn the volume to a higher numeric level and say we turned the volume “up”.). A good example for high and low are a flute compared to a tuba, or a little bird compared to a hippo.
12. Expose your child to different styles of music, both in audio and visual forms. Show them all the things piano can be used for, anything from Mozart (classical) to Gershwin (jazz) to Hisaichi (anime soundtrack). Show videos, go to a performance at a local community college, attend a recital from a studio. Teach your child to appreciate all kinds of music that piano can be used to make, both solo and ensemble. Also remind them that they won’t be as good as the people they see overnight; it takes practice and years of training. Notice the music in movies, at the mall, and in video games too!