Dynamic stretching is executed by gradually increasing the reach, and/or speed of movement of your body. Dynamic stretching consists of controlled leg and arm swings gently taken to the limits of your range of motion. Dynamic Stretching contrasts ballistic stretching in that - ballistic stretching is done by trying to force a part of the body beyond its natural ROM. In dynamic stretches, there are no bounces or "jerky" movements. An example of dynamic stretching would be slow, controlled leg swings, arm swings, or torso twists.
Dynamic Stretching should not be done to fatigue. Tired muscles have less elasticity, which decreases the ROM used in your movements. Continuing to exercise when you are tired serves only to reset the nervous control of your muscle length at the reduced ROM used in the exercise (eventually causing a loss of flexibility).