Thought I would contribute back to POTN and start a thread on shooting with both eyes open. I have enjoyed bird hunting (real gun, not camera) for many years and my Dad taught me at an early age to shoot with both eyes open. Many, if not most, people you see shooting guns have trouble keeping one eye open, much less both. Pretty much same goes for photographers, at least those in the amateur category. So here is a quick 'how to' if you are currently shooting with just one eye.
1. Mount a lens that gives you a 1:1 perspective or field of view
2. Focus while looking through viewfinder
3. Close one eye and open the other while holding camera in place
4. Alternate which eye is open, maintain image composition
5. Attempt to open both eyes and literally see both images
If you have a perfect 1:1 perspective between viewfinder and actual subject, you should not have a problem focusing both eyes on the subject even though one eye is looking through the viewfinder. Focusing with both eyes gets more difficult when the perspective is not 1:1. To remedy this takes practice and training, but the payoff is well worth it! 
For instance, I was shooting a softball game last night and managed to capture several hitters at just the moment they swung the bat. I did this by first composing the image, locking focus, and opening my left (non-dominant) eye so I could see and anticipate the ball entering the frame.
Another instance is shooting kids at a birthday party. I like tight shots of kids faces and pretty much ignoring everything else. However, it's easy to A) lose track of the kid when using a long zoom (70-200 for instance), B) miss action happening elsewhere and C) snap the image just as another kid runs into the frame.
So, shooting with both eyes has its advantages and will definitely increase your keeper rate. I dare say it also helps you keep an open eye to the world around you even while the other eye is peering through that dark tunnel of a viewfinder. 
Some examples:
