I just got back from Yellowstone National Park where the temps were a balmy -16. Burr. Not the kind of day that makes my camera happy.
If you do a lot of outdoor photography in extremely cold weather, you need to have a back up battery so you can keep one battery warm in your pocket while you are using the other one, and keep switching them back and forth as they get too cold to function properly.
Other than that, the trick is just to stay warm and enjoy the wonder of Yellowstone!
Hope you enjoy these snaps.