px_eliezer_ As it's been said fuel is 'ethanolated' which tends to collect water vapour in the fuel system and let it be passed through the engine without causing issues. Keep the tank full this time of year, less air space in the tank means less space for air and thus moisture, and the added weight helps keep the rear end weighed down a little bit more which can be helpful, more so in a rear wheel drive vehicle but still helpful in AWD or FWD. Having extra fuel can come in handy if traffic is crawling along due to the weather or you get stuck. Get a winter car kit, open it up know what is inside and add things like matches, candles, food and water, a deck of cards, good first aid kit. Extra bottle of washer fluid (now that cars have something more volumetric than a pathetic sized piss bag of washer fluid having it is less of an issue but it can come in handy on trips, gas stations overcharge for the stuff.
If you have a block heater use it, helps keep the engine slightly warm. Some people have battery heaters, that could be useful if you have a large heavy engine that needs a lot of cranking power to turn over, easier to install but since most engines are alloys of aluminium and use water like oil temperature (at least at the cold end is less of an issue).
Wiper blocks, it sounds stupid but if you have to park outside and an ice storm happens or your wipers are shoved down in a grove between the wood and windshield that just loves to collect snow and ice they are good for lifting the blades just a fraction of an inch off the glass so they don't get frozen in place.