Stretching is especially important for people who have heel pain, plantar fasciitis, and Achilles tendonitis. You don't need anything fancy, you can stretch against a wall, a tree, or anything that will serve that general purpose. Ideally you want to stand about arm's length away from a wall. Your feet are originally about shoulder width apart, the front leg is in front for balance only--it's the back leg that's being stretched. In the first stretch, your knee is straight. Your heel and your arch are flat on the floor. Almost like you're doing a push-up, slowly lean forward keeping your body straight until you feel a pulling.
Then you go back to the original position and the only difference is that you're going to bend the back knee. Bend that back knee, keeping the heel and the foot on the ground, and then slowly lean forward again. You're going to feel a pulling or stretch around the Achilles tendon. When you feel that slight pull, you hold the position for 30 seconds. Then switch legs and repeat.