Stop looking for dynamic stretching exercises in Google. This list is the only resource you'll ever need to find stretch exercises for ALL your body parts!
CLICK HERE to jump straight to the 101 stretches, or read further to learn more about stretching and exercise in general.
I've heard it time and time again that warming up is a waste of time and energy. The excuse is usually that a warm-up will take away from the energy needed for the actual workout, but that's just not true. Actually it's a great way to get your heart pumping and get you in the right state for exercise.
A good warm-up should last about 5-10 minutes making sure to get the heart rate elevated. When you get your heart rate up, it will start pumping more blood and oxygen throughout the body, including into the muscle tissue. The muscles will become pliable and more flexible allowing for better range of motion and exercise performance.
Warming up also lubes the joints, readies the tendons and ligaments, and has quite a few mental benefits as well.
Stretching is just as important as warming up in most cases. Stretching should be done after the warm-up or you can do dynamic (active) stretching with the warm-up (before the workout).
Either way, it's a good idea to get it done for many reasons. As mentioned before, when the muscles are warm, they are more pliable and flexible. This will allow you to perform better in any activity.