I'm going to be winter camping, and I'm concerned about getting frostbite. What can I do to protect myself?
It is much better to avoid frostbite than to treat it. You can easily lose fingers and toes to frostbite. When you are camping in the winter, you cannot go into the lodge and warm up like you do snow skiing. You should really pay attention to frostbite.
If it is much below freezing and you have numb fingers or toes, you should take some kind of action. If you have more clothes, use them. Chemical foot or hand heating packs work well and can prevent frostbite. You can warm your fingers or toes on someone else's stomach. You might be able to move around a lot and warm up your fingers or toes.
When your body starts getting cold, it reduces circulation to your extremities (fingers and toes) and they get cold. If you can warm up your whole body, it will warm your fingers and toes.
You can also get frostbite on your face if you leave it exposed to the wind. Your face warms up easier than your fingers and toes, though. If you have any numb spots on your cheeks, ears, or nose, warm them up. You can also see fresh frostbite on a face -- it's usually kind of white colored.
As stated above, the best way to treat frostbite is to avoid it all together.
As for proper treatment, you should slowly warm the affected area, typically done through a warm water submersion. Frostbitten feet should not be thawed until you are ready to no longer walk, as you will more than likely lose the use of your feet.
Additionally, in a situation where you are likely to get frostbite you are also likely to get hypothermia. Make sure you study up on the early warning signs of hypothermia. It's a killer.
Make sure you tell people where you are going, when to expect you, etc. if you plan on doing this.
As said, prevention is better than cure. But, most importantly, don't attempt to thaw frostbitten areas if there's any chance of them re-freezing. This typically means don't try to treat it yourself in a back-country setting.
...And once you're in civilization, get a medical professional to handle it!
Very important: Do not exhale air into your gloves/boots or at your hands/feet while still exposed to cold conditions. It may warm them up for a few seconds but since your exhalation contains moisture, your extremities will get wet(ter) and even colder very quickly. Just a simple thing to keep in mind.