Edit: Wonderful information in this thread. Good work comrades! I'm proud of y'all :Care-Comrade:
Mods delete this if there's already a tip thread, but now is the time to share any information we can that can help people. I see good advice in the related threads, but I don't see one that's just dedicated to tips so I'm making this post.
Onto the tips:
If you have a tent, pitch it inside your house. It is a considerably smaller space to keep warm, and your ambient body heat will warm it.
If you don't have a tent, get bed sheets and hang them to create a "smaller room" within a room.
Sleep together in the same room with your other household members and pets. Your body heat will help warm the space.
Put your sleeping bag inside your bed and sleep inside that under blankets. Down comforters are great. Wool is great at insulating if you can deal with the itch and you aren't allergic.
Socks: Put on two pairs of socks, a warm insulating one on the inside and a thinner one on the outside. Put on your shoes (boots preferably) and pull the outer layer down over the top of your shoe. Snow will no longer fall inside your shoe. The only thing worse than cold feet is cold wet feet.
Fold newspaper into inch wide strips and pack it into anywhere cold air can seep in, like the bottom of the door. 3-4 large sheets can be taped over windows to provide extra insulation.
Layers layers layers. If you need to do any work outside peel off layers as your labor begins to warm you up. You do not want to sweat. You do not want to be wet. You can always put the layers back on.
Throw tomorrow's clothes in your bed with you to warm them up so you don't have to put on cold clothes in the morning.
Use every hour of daylight you have to prepare for the following dark. :af-heart:
First aid stuff: Symptoms of hypothermia include confusion/irrationality, no longer shivering, slurred speech, drowsiness, weak pulse, and shallow breathing. Hypothermia comes on in stages and is most likely to become severe if you're wet as well as cold. It's much more likely than frostbite (which takes longer to set in) and is far more dangerous.
If someone you're with is acting unusually sluggish, clumsy, mentally "off" and unresponsive in severe cold weather, you may be tempted to try to re-warm them as quickly as possible with a fire or hot liquids, but a slow and gentle approach is better to prevent them going into shock or (worst case scenario) cardiac arrest. There were a lot of cases in WWII where sailors rescued from the sea would all die like an hour after being rescued, and it was because the doctors were giving them rum toddies and hot soup. Don't be that guy.
Ideally they need to be rewarmed in a hospital, but if that's not possible, remove any wet clothing, cover them with blankets, and use warm dry compresses (like towels warmed next to a heat source) on their neck or chest. If they can swallow, give them something warm that contains sugar (NO ALCOHOL alcohol is not your friend in the cold).
To add to hypothermia stuff: If you think it might be coming on, here's a quick test. Press down on one of your fingernails, then release. If the color hasn't returned in 2-2.5 seconds (the length of time it takes to say "capillary refill"), you need to warm up.