In an interview with Mrs. "A.", mother of three successful Music Place students, Resource Specialist Beth Smith gleans the following practice tips that have worked for her kids--

Make practice time a habit: every day, same time
Recommends morning before school – that way they don't have to do it after school when they are tired
Make task part of chore list and connected to their weekly allowance
Have older kids help younger kids (offer an incentive which pays off right away)
Keep expectations reasonable and age and level appropriate (such as “play each assignment 4 times”);

Increase practice goals as they mature and progress
Keep in mind: we most enjoy the things we are good at!
She goes on to comment that parents who are too lax about helping their kids develop good practice habits undermine their own investment; parents need to be as committed as the student, or even more so. I tell my kids, "I am giving you a tool in your toolbox for life” by having you take music lessons. It's up to you what you decide to do with it when you grow up.

“I wish my parents would have done this for me.”

Incentives are okay! Just like adults, kids feel good when they experience payoff for their hard work. Not every expected behavior in life should be externally rewarded, but it's helpful for tasks that are challenging.
Eventually you won't need to offer rewards – the joy of proficiency will become a reward in itself.
Mrs."A"'s kids started at The Music Place in 2008 when her oldest daughter was 4 years old. All three continue to progress and impress audiences when they perform.

--from an interview by Beth Smith, Educational Resource Specialist