If you fall out of a window, or from a great height, it is possible to save yourself, or at least escape serious injury.
As you fall, try to cling to anything you see. This will delay your fall for a while and decrease your speed a bit. If there is a plastic or glass canopy on your way, it can help break your fall.
Try to relax your muscles while you are falling, instead of tensing them. Drunk people or little children often have the best chance of surviving a fall. This is partly because they are unaware of what is happening.
Also, alcohol will reduce fear, helping a drunk person to relax their muscles. Children's bones are softer than those of adults, and more likely to deform than to crack after hitting the ground.
Slightly bend your knees and hold your legs together. This helps both of your legs touch the ground at the same time. Also, try to land on the tips of your toes, keeping your legs spread apart instead of straight. Landing on one leg will not necessarily protect the other.
As you fall, don't forget to cover your head with your arms. When your feet hit the ground, you will bounce a little before you come to rest. If you can fall on one side, your arms will protect your head from the impact.