It depends on where you're staying but these would be the most ideal pointers.
(1) Stay dry. That includes sweating. Don't bundle up so much that you are sweating endlessly. It will act as a conduit and the heat will be sapped away from you. If you can afford it, get water/sweat wicking thermal gear. Walmart has UnderArmour knock offs that fit this bill. I can go outside in below 0 weather with just shorts and my long sleeve, off brand thermal and still be comfortable enough, at least long enough to get the mail, start the car and smoke a j.
(2) Shelter. If you have a free standing back packing tent, then you're kind of already set, but just in case you might want to look into DIY survival shelters
http://www.practicalsurvivor.com/urbansheltercoldweather &
http://www.motherearthnews.com/diy/winter-shelter-ze0z1301zsau.aspxand how to set them up with the land so you can give yourself a break from the elements. Exposure, more than hunger, is deadly in it's own right. Fire is also helpful but might be prohibited.
http://survivial-training.wonderhow...re-from-your-enemies-dakota-fire-pit-0116303/ This is a super informative article on how one would conceal a fire, tips on wood to use that produce the least amount of smoke and what not. I haven't read it all because it is really long, but in you're case it will pay off. If you're able to establish a semi-permanent squat, try scoring some wool insulation and build a cot or something to get you off the cold ground.
(3) Food. Stock up on high carb/calorie foods, you're going to be too busy shivering away your energy to be concerned with figure. Your immune system will also be more susceptible during the colder season so make sure you're also getting a whole diet (or close) with vitamins. I listed a resource here not too long ago on how one would go about getting excess food from gardeners:
https://squattheplanet.com/threads/site-for-finding-fresh-produce-for-free.26873/
(4) Clothing. Learn the core components of layering and how to layer for different weather events:
https://www.rei.com/learn/expert-advice/layering-basics.html. DO NOT FORGET your feet and extremities. I'd rather have warm boots, socks over a tent any day. Get yourself some gloves.
Your head is going to be where most body heat leaves, so a beanie like mine, maybe a bandana or neoprene face wrap when it's windy and definitely a cozy hoodie.
If that sounds like too much work?
Hitch South.