Long underwear - preferably wool but that's very hard to find in most stores; for a weekend, the regular cotton long johns should do. I have a fairly expensive pair of wind pants with a full-length zipper down each side, so I can take them off without removing my boots, but that's mainly of use if you're going to be in and out of a warm environment (e.g. taking the bus to work).<br><br>One tip I read, but haven't tried, is to drink a cup of hot chocolate with a chunk of butter melted into it. The theory is that the hot chocolate provides a quick burst of energy; the fat in the butter provides a sustained energy burn over a longer period of time. I got this from Garrett and Alexandra Conover's book, The Winter Wilderness Companion - Traditional and Native American Skills for the Undiscovered Season. (448 Pages, ISBN: 007136417X) They claim that the first time they tried this was in Northern Quebec with the temperature around -40. Within minutes they were feeling toasty warm from the inside out. <br><br>I found this an interesting book - I hope to put at least some of their theories to the test this winter. The authors are professional guides in Maine who run winter snowshoeing expeditions in Northern Quebec, and they seem to know what they're talking about. I'm not affiliated with the book, the authors, or the publishers in any way. It's available from Amazon - their web site says they have 4 left in stock but more are on the way.<br><br>Also, if your companions bring along a "pee bottle" so they don't have to get up in the cold early morning to urinate, they'll probably be a lot more comfortable. Make sure it's not glass, or anything that is likely to shatter due to sudden temperature variation; and that it won't leak. These can double as hotwater bottles to be used for first aid for hypothermia, as well; fresh urine is generally at the optimal temperature for warming someone up, and the bottles fit naturally into the groin, neck and armpits, where the heat transfer is fastest.