In my experience, I benefit from the following:
-- Keep weight down. As the study showed, the impact weight is a multiple of your actual weight. If you gain 5 lbs, the strike force on your knees increases by 8x5 = 40lbs! I certainly feel it when I gain a couple of pounds!
-- Don't run on pavement, run on dirt and/or grass. The less flexible thensurface, the greater the impact stress force will be.
-- If you're not a barefoot runner, wear gel or other cushioned insoles.
-- Pay attention to your stride, foot strikes and posture.