Done it, it's hella fun! Make sure your sleeping bag is warm enough, and bring a tarp and a sleeping pad. Pad is essential to staying warm so you're not laying directly on the cold ground or snow, and you can wrap the whole package–sleeping bag, pad, and you- in the tarp to stay dry.
Building a fire is a great idea too, but you probably want to do that outside the shack unless you've got some good ventilation figured out. When we overnighted in our smoke shack, the chimney didn't work and we smoked ourselves out for a while (insert 'smoke shack' jokes here).
Liquor is also essential, I recommend whiskey. And candles, and good buds.