Kids today start playing very early compared to my generation -- I started at age 9. These days, it is common to start at 4 or 5 years old with light balls and racquets and on miniature courts.

Obviously the earlier a kid starts the higher chance he/she has of excelling, but it has to be monitored by the parents to prevent burnout or overworking the child.

It is important to start with short sessions of 30-60 minutes no more than twice a week and to combine it with other sports.