From experience and from what others have told me, I think the best way is to land toes down first.  Aka not on your heel and not really even on the ball of your foot.  Your toes hit first then everything follows (you have to kind of point your foot down while its in the air to do this).  For me, this means I am lighter on my feet and less likely to hurt something by landing on rocks or whatever.  I don't know how long he's been barefoot running but it takes awhile to build up muscles and tendons and stuff to be able to really cruise downhill, especially on trails.  Then its pretty natural.