Watch for moisture. When taking a shot, take care not to exhale near the lens. Look away from the camera, or take a step back, before exhaling. Otherwise, condensation will freeze to the surface of your lens instantly. Some companies make dehumidifying lens caps, which can help with that problem. It’s not a bad idea to keep silica packs in your camera bag at all times and change them occasionally.
Bracket your images. Whenever I find myself in a situation where time is of the essence, I bracket. It's a huge help to not have to mess with auto-exposure compensation when it's really cold out. That, and often cold means there's bright snow around that's hard to expose properly anyway, so you might be very glad you have the extra frames. Try to rely on your histogram as much as possible to get a clear idea of how bright your image really is.
Insulate metal parts. Touch an aluminum tripod with bare hands in cold weather, and you’ll quickly learn you never want to do it again. If you’d like to save your fingerprints, prep the metal parts of gear that you might be handling without gloves. It's helpful, for example, to cover your tripod legs with some sort of insulation, such as hockey tape or foam.
Keep food and hot drinks handy. Eating a lot will keep you going for much longer. But if the food is hard to access, you might not bother to dig it out. I like to keep something energy-rich in an easily accessible pocket, such as nuts, dried fruit and (my favorite) chocolate. A thermos with something hot and sweet will keep you warm from the inside out and help you to avoid some serious consequences of cold, such as hypothermia.
Use two camera bodies. Changing lenses can be a real challenge in cold, wintery conditions. Handling gear in the cold is hard enough, but when you change lenses you also risk exposing your sensor to moisture. If you have a backup body, consider going out with two cameras so you can shoot at different focal lengths without having to switch lenses.
Take advantage of conditions. Some unique features come out only in cold weather—keep an eye out for them! These include methane bubbles in lakes, hoar frost, the interplay of sidelight and dramatic temperature differences (such as fog over open water), icicles, long shadows and the softening effects of an untouched blanket of snow. Sometimes this means venturing out in the coldest temperatures imaginable, but I promise you’ll go home with images you’re proud of.
Seal it. Depending on your gear, you may need to be cautious about drastic temperature differences, such as when you return to heat blasting in your car or go back indoors. Before exposing your gear to that warmth, it’s recommended that you place it in a sealed bag (such as a Ziploc) until it has reached room temperature. This will prevent condensation forming on the camera and lens. Add a silica gel pack to the bag to further cut down on moisture.
