Heel spur and plantar fasciitis are often caused by short muscles, especially in the calves and footsole. It is therefor important to make these flexible and longer again, as these short muscles cause a constant strain on the plantar fascia, and this must be avoided. Stretching is very important then.
Several stretching exercises are possible to treat the heel spur, the most advised ones are listed here. It is not necessary to do all of these, as some exercises have a similar effect. Just experiment to find out which one fits you best. Make sure to find a good balance, stretching all muscles involved.
Make sure not to exaggerate, stretching too hard can damage muscles and tendons. All of the exercises should be repeated a few sessions a day, performing 2-3 sessions of 10-15 repetitions per session.
Exercise 1: Stretching the plantar fascia and the calves: stand on a stair step or a bench with your toes, with the heel hanging down. Lower the heel until you feel a stretch. Maintain this a few seconds and let go. Repeat this a few times.
Exercise 2: Stretching the plantar fascia and the calves: Sit down on the floor with your legs stretched out in front of you. With a towel around you toes, pull them towards you until you feel a stretch.
On top of these stretching exercises, it could also pay to increase strength in your lower legs, using these exercises.
Exercise 3: Stretching the plantar fascia and: Sit down on a chair, cross your right leg over the left one. Then grab the toes of the right foot with your left hand and pull your toes towards you.
Exercise 4: Stretching the calves: Lean forwards against a wall or a pole. Leave one leg stretched behind you and place the other one bent under you. Then lean further forwards untill you feel a stretch in the behind leg.
Exercise 5: Again lean against a wall, placing both feet behind each other. Then slowly squat down, bending BOTH legs. You will feel a stretch deep in the calf of the behind leg, the so-called "soleus".