Stretching is one of the most popular ways to warm up or cool down for an activity. Stretching is actually one of the most ineffective methods of warming up or cooling down. Many studies have shown that stretching does not decrease the chance of injury when used as a warm-up or cool-down. Warm-ups and cool-downs should be personalized to the individual and activity.
Stretching is good for increasing range of motion or flexibility. The most effective way to stretch is to do it after a warm=up and then hold the stretch for 30-60 seconds.