1-Get your tent protected from the elements. Dig your tent 2 or 3 feet into the snow. Even if it is not windy, the difference in warmth will be noticeable. There’s a reason igloos are warm!
2-The more layers below you, the warmer. On-top of your tent floor you’ll want to have a survival tarp, a wool blanket, then your mattress.
3-Eat lots of fat, protein and carbs. Your digestive system will act similar to a furnace by heating your body. Eating properly and staying hydrated can greatly increase body temperature.
4-Layer your clothes properly. Note: Cotton is a bad idea in winter. Here is a quick summary:
1st- Base layer: something that will wick sweat.
2nd- Insulation layer: something that will keep you warm.
3rd- Outer layer: something that will keep you dry.
5- MULTI TIP
1- Change your socks, change your base layer as they may be sweaty
2- Always wear a something on your head
3- Do a few jumping jacks