These include three different stretches performed for the calves, hamstrings, and inner-thighs, but they are all performed in very similar positions and I do all three stretches (in the order given) for one leg before performing them for the other leg. You will need an apparatus for this stretch: a bench, or a firm bed or couch (or you could use two chairs with your butt on one chair and the heel of your foot on the other) that is at least 12 inches off the ground (but not so high that you can't sit on it with out your knees bent and the sole of your foot solidly on the floor). The bench should be long enough to accommodate the full length of your leg. Sit on the bench and have your leg comfortably extended out in front of you (your heel should still be on the bench) and the other leg hanging out to the side with the leg bent and the foot flat on the ground.
With your leg extended directly in front of you, face your leg and bend it slightly. Place your hands around the ball of your foot and gently pull back so that you force yourself to flex your foot as much as possible. Hold this stretch for about 20 seconds (don't forget to breathe).
Now for the isometric stretch: in this same position, use your hands to try and force the ball (and toes) of your foot even further back toward you while at the same time using your calf muscles to try and straighten your foot and leg. You should be resisting enough with your hands so that no actual foot (or leg) motion takes place.
Now that our calf is stretched, we can get a more effective hamstring stretch (since inflexibility in the calf can be a limiting factor in this hamstring stretch). Still sitting on the bench in the same position, straighten your leg out while trying to hold onto your outstretched leg with both hands on either side as close as possible to your heel. Starting up with your back straight, slowly exhale and try to bring your chest to the knee of your outstretched leg. You should feel a "hefty" stretch in your hamstring and even a considerable stretch in your calf (even though you just stretched it). Hold this stretch for about 20 seconds.
Now for the isometric stretch: when you have gotten your chest as close as you can to your knee, try and put both hands under the bench by your heel (or both hands on opposite sides of your heel). Now grab on tight with your hands and try to physically push your heel (keeping your leg straight) downward "through" the bench, the bench will provide the necessary resistance, and should prevent any leg motion from occurring.
You should still be sitting on the bench with your outstretched leg in front of you. Now turn on the bench so that your leg is outstretched to your side, and you are facing the leg that is bent. You may perform this next stretch with either your toe pointing up toward the ceiling or with the inside edge of your foot flat on the bench with your toe pointing forward (but flexed), or you may try this stretch both ways since you will stretch some slightly different (but many of the same) muscles either way. I prefer to keep my toe pointed towards the ceiling because I personally feel that the other way applies to much stress to my knee, but you can do whatever feels comfortable to you.
Note: If you are using two chairs instead of a bench, the first thing you need to do is to make sure that one of the chairs supports your outstretched leg somewhere between the knee and the hip. If the support is being provided below the knee and you try to perform this stretch, there is a good chance that you will injure ligaments and/or cartilage.
Place your hands underneath the bench directly under you (or you may keep one hand under the portion of the bench that is below the knee of your outstretched leg) and pull yourself down and forward (keeping your back straight) as if you were trying to touch your chest to the floor. You should be able to feel the stretch in your inner-thigh. Hold this for about 20 seconds.
For the isometric stretch, do the same thing you did with the hamstring stretch: keep both hands underneath you as before and try to force your foot downward "through" the bench.