Set up in front of a cable machine by standing in front of the weight stack on a stable raised platform. Your feet should be close together and only your toes on the platform. You will need to strap the the cable "harness" around your waist and hold on to the cable apparatus (holding the handle bars or simply the frame of the machine). This is your starting position.
Raise yourself up using only your toes. Go up as high as you can. Keep your legs straight and locked-out at your knees at all times. Once at the top, lower yourself back down as far as you comfortably can.
Finally, repeat the entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Keep your legs straight at all times to put maximum emphasis on your calf muscles
Don't do this exercise if you are an absolute beginner; there are many other more appropriate calf exercise for beginners such as standing calf raises
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or increase the weight.
This exercise is a great exercise for the calf muscles. Calves are often neglected and most people do not introduce enough variety into their calf work (exactly what is needed to get them bigger).
Thus, this exercise is the perfect exercise to do when your calf workout gets stale and in need of change. The only thing that might present a problem is the body strap (the one that goes around your waist as depicted in the animation above). Most better equipped gyms will have it, but some smaller fitness centers may not. In any case, you can easily buy your own because it's fairly inexpensive to own.