What Smilingcat said. Practice picking your eyes up. I have a friend whose mantra on the motorcycle is "look up 10°." Honestly if you're looking at your front wheel, you should be looking up more like 45°. But you get the picture. Looking at the ground is a sure way to wind up on it. (Just as target fixating on any obstacle - tree, car, lamp post, etc. - is a sure way to wind up hitting it.)

I'm told that mountain biking is a great way to improve your descending skills and learn to "look where you want to go" (not just descending, but all the time).