I am currently on physiotherapy, and one of a very good stretch for calves, hamstrings and perhaps back can be done by straddling a belt on your foot (more towards the toes) and raise leg at 90 degrees (that is if you can, of course) hold the belt and gently pull towards you while your leg is straight. A good stretch should be around 30 seconds (that is if you can hold on tht long again)
For an easier stretch, you can pull your knee to your chest, one at a time while the other leg is stretched up or gently bent.
You can stretch your quads by laying on your side, pull the top ankle to your back end. Turn over to the other side for opposite leg.