Choose appropriate exercise according to your age, health status and what you enjoy.

Never overdo it. Your body will tell you if it's too much.
Remember to do some warm-up activities before exercise.
If you are too tired or sick, don't force yourself to do vigorous exercise.
Stop exercise and consult the doctor immediately once you feel pain, fatigue, dizziness, nausea or breathing difficulty.
Wear comfortable clothing and shoes during exercise.
Notice the weather condition when you play or exercise outdoors.
Notice the temperature change. On hot days, drink enough water during exercise. In cold weather, wear warm clothes that can be put on or taken off easily.
Don't exercise in a wet or dark place to decrease the chance of having an accident.