Get engine driveability problems (hard starts, rough idling, stalling, diminished power, etc) corrected. Cold weather makes existing problems worse. Replace dirty filters - air, fuel, PCV, etc.
Put a bottle of fuel de-icer in your tank once a month to help keep moister from freexing in the fuel line. note that a gas tank which is kept filled helps keep moisture from forming.
Worn tires will be of little use in winter weather. Examine tires for remaining tread life, uneven wearing, and cupping; check the side walls for cuts and nicks. Check tire pressure once a month (let the tires cool first).
Replace old blades. If your climate is harsh, purchase rubber-clad (winter) blades to fight ice build up. Stock up on washer solvent - you’ll be surprised how much you use. Carry an ice-scraper.
Carry emergency gear: gloves, boots, blankets, flares, a small shovel, sand (or kitty litter), tire chains, a flashlight, and a cellular phone. Put a few “high-energy” snacks in your glove box.