In the stretch demonstrated in the images above, the heel should be on the ground and the toes on the wall. Place the unaffected foot behind you. Keep the legs straight and move the entire body forward. Do not move your upper body forward and stick your backside out. You should feel a very strong stretch in the back of the calf and some stretch in the arch.
To increase the stretch, move your heel closer to the wall and increase the angle of your foot. To decrease the stretch, move your heel back and lower your toes. Hold for 60 seconds and repeat 3 times.
You can do this same stretch by using a large book or block of wood. Stand on the book with your toes and drop your heels to the ground, supporting yourself against the wall. In the very inflamed stage, this stretch can aggravate the pain, so be cautious in the early stages of plantar fasciitis. Don't hang your heels off the back of a step to stretch your calf if you are injured like the photo below.
Do not stretch through pain. None of these stretches should be painful.