The first and foremost goal in winter photography is keeping yourself safe and warm. Protecting your investment in camera gear is also important. Both are critical for a successful winter outing with your camera.
Start with a moisture wicking thermal base layer. Polyester and merino wool blends are good choices. Next a mid layer of wool or fleece will keep the warmth close to your body and that all important water proof outer shell will keep you dry and protect you from the dreaded wind chill. The choice of outer layers depends on the type of photography you are planning. Choose a heavy lined jacket if you are going to be sitting for long periods watching for wildlife, or a lighter waterproof and windproof jacket if you will be consistently on the move. Gor-Tex is a popular material for the outer shell because it can provide comfortable ventilation and 100% moisture protection at the same time. Protecting your feet from the cold is also important, so choose lined boots for deep snow and severe cold or Gor-Tex hiking boots in light snow and moderate cold. For extra deep snow or ice, snowshoes or crampons are a good choice for back country photographers.
Protecting your camera gear is also important so a quality rain cover for your camera and lenses is critical if it is going to be snowing or raining. There are many choices for photography rain gear costing from just a few dollars to hundreds of dollars depending upon your situation. The choice of rain cover depends largely upon the lens or lenses you will be using. An economical plastic cover from the camera store may be enough to protect your camera with a small wide angle or 50mm lens attached, while a heavy duty professional cover such as Aquatech rain gear may be required to protect a big lens with a large lens hood in arctic conditions.
Invest in a good waterproof backpack photography case to protect the rest of the gear you bring along. Lowepro makes a fine line of rugged outdoor camera backpacking gear. Store your extra batteries next to your body to help them retain a strong charge. Use a high quality lens filter to keep moisture off your glass.
For hand protection wear a high tech glove liner on your shooting hand and keep it inside the camera's rain cover for protection from the wind and precipitation. The light glove liner allows you to feel the camera controls while keeping your hand warm. Keeping the shooting hand inside the rain cover keeps the glove from getting wet and causing water to seep into the shutter button. Wear a Gor-Tex windproof and waterproof glove on the other hand. Viewing the camera controls in heavy snowfall with a rain cover on the camera can be nearly impossible, so pick a setting before you start that will yield a good exposure in all conditions. An auto setting including 400 ASA and exposure adjustment of +1 will work well on those gloomy overcast days with a lot of white snow in the background. If it has one, use your camera's locked setting for exposure adjustment, shutter speed and aperture controls to assure that your exposures stay within acceptable range.
Even if the winter weather turns foul, with proper preparation there is no reason why you shouldn't continue to enjoy your passion of outdoor photography.