With all the foot problems I see that come through my door, the most common denominator is that people have tight calf muscles and in general, tight posterior leg muscles.
These muscles include the calves, the hamstrings, the gluteal and hip muscles.
Common stretches for these should be directed at stretching them for 10 seconds, 3 times each muscle area daily. A great time to conduct these would be at night or in the morning when the patient is already lying down in bed. These are meant to be simple, relaxing and pain free. If it hurts, you most likely are stretching too hard. Everyone should stretch at their own pace and distance. Never force the stretch.