Winter backpacking tips
Wow, lots of people have mentioned some good stuff... I haven't done a done of backpacking in extreme winter conditions, but generally speaking; you may spend a great deal of time in your sleeping bag. It's either some of kind of entertainment at night (cards, reading books, listening to music, etc...) or getting ALOT of sleep. It can be VERY helpful to make sure your body is warm when getting in your sleeping bag. As I understand, the bag traps your body heat, it doesn't neccessarily "warm" you up. As others have said, when you arrive at camp, IMMEDIATELY get out of your wet clothes (use the "dryer method" of dry clothes next to your skin, damp/wet clothes over top of them) get warm if you've chilled down (run around, push-ups, jumping jacks, etc...) and GET IN YOUR BAG.
It seems like it takes forever to do things in the winter (as compared to the warmer months) If your planning on tenting, tent poles may freeze up at night and getting them apart could be just another little challenge. Often blowing warm air on them may aid in the "defrosting" process. I haven't seen many people use filters/purifyers in the colder months because they can freeze up. Start your trip well hydrated (as true in any hike in any season), use iodine (allow longer times because the water is that much colder), and be careful if you bring a bladder kind of carrying system for your water. I've seen the hose freeze up solid in very short time (even the insulated ones) Nalgenes work well because you can put boiling water in them. Ah.... here's an idea, boil water at night, put in nalgene (make sure lid is on and doesn't leak!!!!!!), put in sleeping bag to pre-heat bag while you're out taking care of nature's call and believe it or not, you've not only purfied your water, but got some heat going in your bag. Speaking of the call of nature, how does one abide to the rules of Leave No Trace when "dropping the kids off at the pool" ie, taking a dump. Seriously, digging through lots of snow, digging a 4-6" dia. hole, 6-8" deep away from water sources in frozen ground, something to think about.. We're tallking about some work here, for sure!!! Is this possibly why when the snow melts in the late spring one can find TP and brown turds lying on the ground? Not to be crude here, but what do others do about this matter? Personally, I try to "take care of my business" in privies when I can.
As others have stated, you develop a "system" that keeps you comfortable and in really bad situations, ALIVE... No joke here, traveling/camping in the winter can be EXTREMELY dangerous... Lots of people have perished in the mountains (I live in the NH's White Mtns.) because of poor judgement, fatigue, and lack of knowledge, among other reasons. It sounds like you're going with a small group which is an excellent idea for emergency reasons. As in any hiking/backpacking trip, leave a iternary with a friend/family member and tell them you'll call them when you get back.
On the flip side, traveling in the winter can be a total blast with the right kind of attitude (and traveling campanions). It's very rewarding, makes for great stories, and can be a great workout. Have fun, stay safe, and post a thread as to how things went for you and what "systems" you developed for yourself.
Youngblood