This exercise is excellent for foot and heel pain. You will need a towel or something similar to perform it.
Sit on an exercise mat or on a bed. Roll a towel and place it on the ball of your foot so that you can stretch the achilles tendon on the back of your foot as well as plantar fasciitis. Keep your knee straight and leg on the floor. Pull until you feel a stretch and hold for one minute, and then switch and do the other side.