>>Flatten your sleeping surface
As soon as you climb into your tent, use your knees to smooth out the area under your pad. "Don't wait until later to do this," Larsen says. "Once the snow melts and refreezes, it's hard to manipulate. I also create a shallow trough for myself so I don't roll around."
>> Bring a closed-cell foam sleeping pad
Even a warm bag is a cold bag without a good, insulated pad underneath it. Most air mattresses only insulate down to about 30°F. If you want yours for comfort, lay down a foam pad (A) first, like the Therm-a-Rest Ridgerest Solar (p. 68).
>> Put your partner's pad close to yours
Less cold air will rise through the tent floor. Better yet, connect them with the Big Agnes Sleeping Pad Coupler Strap (B) ($10, bigagnes.com). Place stuffsacks and extra gear around the tent's inside perimeter to further insulate.
>> Stash your boot liners in your bag
Nothing hurts more than trying to ram your feet into frozen boots in the morning. Also, stow electronics, batteries, fuel canisters, and anything else you don't want to freeze (C) (buy a sleeping bag with a little extra length for this purpose).
>> Don't burrow deep into your bag
"Moisture from your breath will get trapped in the bag," Larsen says. "Instead, cinch the draft collar and close the hood down around your mouth and nose so you have a blowhole to breathe through" (D).
>> On high-wind nights, sleep in shifts
"Someone will have to check the tent's rigging every few hours," Finnegan says. "If you wait too long to tighten a line [because you don't want to leave your warm bag], the damage to the structure will be impossible to control."
>> Munch on a midnight snack
"If I wake up cold in the middle of the night, I wolf down Strawberry Clif Shot Bloks ($2 for six, clifbar.com) to fuel my engine," Larsen says. Other calorie-dense foods like chocolate (E), cheese, and nuts work, too.
>> Prevent spills
Put a straw near your water bottle for no-mess drinking in the middle of the night (F).
>> Be prepared for frost in the morning
On freezing nights, water vapor often condenses on the tent's inner walls, your sleeping bag, and packs, even with the door cracked. Once the ice melts, it will sop your gear. Control frost by keeping your gear covered or inside garbage bags, and by sweeping (with a tent brush) ice crystals into collectable piles before they melt.
>> Don't hold it
If nature calls in the middle of the night, don't procrastinate; this makes you colder in the long run because your body has to burn calories to keep urine warm. Guys should consider using a designated pee bottle (G) (mark it with tape or some other feature). Girls, don't even bother; aiming is dang tricky. (For a review of pee gear, see backpacker.com/funnels.)
>> Bundle up your water bottles
"I use Granite Gear's Air Coolers (H) to keep my water from freezing at night," says Larsen (one-liter size, $22, granitegear.com). They also work to insulate hot drinks or soup.
>> Heat up your bag
Put a hot water bottle in your sleeping bag at night, and it'll radiate heat like a sauna stone (I).