This is such a neglected area for many people. Start off right and take the time to stretch AFTER every workout. In the beginning stretches should take at least 5 minutes. As you increase distance and pace you will probably need to stretch longer.
Important rules for stretching:
Never stretch cold muscles. The best time to stretch is after your walk.
Do not bounce. Go into a stretch slowly and hold gently. Stretch to the point of feeling a gentle pull, but never to the point of pain.
Hold each stretch for 15 to 30 seconds.
If you have problems with a particular area stretch that area twice. Be sure to stretch all the major muscle groups, and put extra focus on any areas you have trouble with. Find a few recommended stretches below:
Calf Stretch -- Stand on your toes on a step or curb. Hold on to something for balance. Remove your left foot and slowly allow the right heel to move down. Hold this position. Be sure to keep you body upright and straight. Release and repeat on the other side.
Another calf stretch -- Take a big step forward with your left foot, keeping you right heel on the ground. Hold the position and repeat on the other side. Be sure to keep your body upright and your abs tight, do not arch your back.
Hamstring and Lower Back -- Slowly bend forward from your waist with one knee slightly bent and the other straight. Do not let your head drop. When your chest is as close to your knee as possible, point your foot (straight leg) slightly. Repeat on other side.
Quadriceps Stretch -- Standing up, hold on to a stationary object. Bend your right knee, bringing your foot toward your buttocks. Keeping your left knee slightly bent, grasp your right ankle with the hand. Slowly pull your leg up and back, bringing your foot at high as comfortable. Repeat with other leg. (To protect your knee... think of pulling the quads back rather than pulling the foot toward your buttocks.)
Shoulder Stretch -- Standing upright, cross left arm over chest. Place your right hand on your upper arm and pull arm in tight to chest. Be sure to keep shoulders down and do not pull at the elbow. Hold, and then repeat stretch with other arm.
Neck Relaxer -- Turn and look over your right shoulder and hold. Repeat on the left side. Don't hyper-extend the neck, or tilt it backwards. Next, gently drop the head so that the ear goes towards the right shoulder and hold. Return to upright position. Repeat forward and on the left side. Keep the spine in an upright position and don't hyper-extend the neck, jerk, or tilt the head backwards.