Be in proper physical condition before they play a sport.
(A preparticipation physical,especially for older children, is important, says Purvis, to screen for undiagnosed heart ailments).

Know and follow the rules of the sport.

Wear appropriate protective gear -- such as shin guards for soccer, a hard-shell helmet when facing a baseball pitcher, a helmet and body padding for ice hockey, and properly fitting shoes whatever the sport.

Know how to use athletic equipment -- for instance, how to adjust the bindings on snow skis.

Always warm up before playing.

Avoid playing when tired or in pain.