Know Your Camera
Every camera comes new with a nice thick manual that covers everything you need to know about how to operate it, right? Wrong.
Reading it is a great start, but the real learning doesn't happen until you are out in the field using the camera. Try new things with it, especially during quiet times when you're not otherwise busy with shooting. Getting more familiar with your camera's operation when you have the luxury of taking your time can go a long way towards being able to operate it as second nature when the action heats up. When the sun is setting or when a deer is walking through a meadow is not the time to have to stop and read the manual to figure out how the controls on your camera work. You need to be able to react quickly to get the shot sometimes.