Try to land on all eight wheels. When you hit that ground, you're doing so with a lot of force. It's at this point that you turn into a human shock absorber. You want to take most of the force in your knees. Do this by bending them.
Many people make the mistake of bending their back down instead of their knees.
If you do that, your back takes the shock. That's when it hurts, espeically, if you're like me and have chronic back and neck pain in the family. Notice that I'm practically knealing on the ground. That's what I'm doing, and as a result, slew the nasty Shock Monster. There are four crucial elements to remember when jumping.