I know this might sound weird to some, but the best way i know of teaching someone to look at movement is to find a really and I mean really good western pleasure horse and watch the way the front ends travel. That foot should reach out in front of the knee and look as if its floating in air for a second before it hits the ground. If this is happening it means there must be enough slope to the shoulder to allow the knee to flex and enough set in the pastern to allow the foot to travel naturally. If all this is going on your calf is not too straight, hence won't buck over.
Joshua