Daily practice will insure the most progress and will keep frustration to a minimum.  

Do not expect your child to carry out his/her practice entirely by him/herself until about 10 years of age.  

Piano study is a significant commitment for the entire family, and requires patience and consideration from everyone in the home. 

Practice is repeating a small portion of a piece or technical exercise with a specific goal in mind.  It is not mindless repetition.  Divide practice into two 15 minute sessions, but do not watch the clock.  Rather, set goals to accomplish during each session.  Set specific times to practice each day, and ask other family members to vacate the piano room during practice time.  

It is a wonderful idea to play a concert once a week for the family to show all how much improvement was gained during the week of practice.

After you return home from a lesson, sit down with your child and ask him/her to play through the lesson assignments one time.  Ask your child to describe what he is supposed to do and why and then have him play it for you.

During the daily practice time, the student should work for control rather than speed, consistent fingering, and small, reachable goals each day, such as mastering the notes and rhythm of a phrase by using the metronome set on 60 and increasing the setting only gradually as the student is able to play the phrase with ease.

Attitude is vital, and desire must be present!

See http://www.serve.com/marbeth/helping-kids-practice.html for more helpful ideas.