DROM (dynamic range of motion) befor your workouts and ballistic after. Warming up is essential and I'll argue it er.... discuss it with anyone who see's otherwise. DROM exercises can be worked into your warm up as well.
DROM exercises will increas blood flow to muscle, increase fexibility by in effect wakeing the entire muscle up, not decrease muscle response/speed/agility and prevents injury. About 90% of injuries that are attributed to "not stretching befor" are from not warming up. And face it anybody too lazy to stretch befor physical activity is damned sure not likely to warm up either.
Ballistic stretching is actually semi traumatic to the muscle and will cause it to tighten up agterwards. Not exactly a desirable thing when going into a physical activity. But ballistic movements are great for a cool down/after activity stretch. These stretches are what add to your flexability and are best done when a muscle is warmed up and compliant.