When referring to keeping the head down, picking the head up, or sliding in front of it, we are really talking about keeping the top of your spine behind the ball at impact. This will, in turn, keep your head down through the swing.
A couple tips to help with this problem are to slow down and stop trying to hit the home run or, in our case, the 300 yard marker. If a shot is properly hit, you should see the ball when it is reaching its highest peak. If this happens, you have hit a solid shot.
I encourage you to watch good players and see where their head is positioned during the swing, especially at impact, and shortly after impact. You can clearly see in this photo that he did not peek at impact.