Just behind the ball of your foot so as to load your arch in a downward motion. Your heel will almost definitely touch the ground. This, as opposed to a forefoot strike, where you're landing just behind your toes and loading in a rearward motion (think sprinting). Your heel probably will not touch the ground.

Both of these are hard to do in typical "running shoes" which build a significant amount of rubber into the heel, while also being fairly thin up front.