Maintenance

There are some simple things which I have never done in the past but will do from this point forward.

Petroleum Jelly
Applying petroleum jelly (Vaseline) to rubber components like weatherstripping, tires, etc. keeps the rubber soft. There is a 99% chance it is recommended in the owner's manual for your car. This isn't just something limited to cars, though! Any rubber item you own which is exposed to the elements can benefit from this simple practice.

Checking Fluids
There is no practical reason to skip checking your engine fluids when you fuel up your car. It takes all of 30 seconds to check your oil, and mere visual inspection for coolant/antifreeze, brake fluid, and power steering fluid. Even during the coldest days of winter this will not keep you out in the wind and snow long enough to be unpleasant.

Car Washes
It seems like vanity to hit up the wash for your car to become filthy again in such a short time. Things are worse during the winter, since sand and possibly salt end up all over your car daily. But this is precisely the reason you need to wash your car! Sand can be damaging to your cars finish and salt will cause rust. North Dakota, where we live, does not salt their roads, but we routinely drive on the Minnesota side where salt is applied liberally. It is optimal to be able to dry your car thoroughly after washing, specially in winter. For this reason, it is handy to have access to a heated garage.

Tire Pressure
My front tire pressure was off by 10psi. Ten pounds! This makes a difference in fuel economy as well as in the life of the tire. A tire gauge only costs a few bucks, and most gas stations will let you use one for free if you ask. Air is also generally free at gas stations.

Fuel Economy
Keep a log book in your car to track your fuel economy and to keep notes about car performance and maintenance. Every time you fuel up, take a minute to jot down how many gallons you put in and what your mileage looked like. It is easier to spot potential issues when you can see fluctuations in your average fuel economy over time. If you ever sell your car, you will have valuable documentation containing a record of every time fluids were changed or topped off, parts replaced, and even unresolved issues. A smart buyer would kill for this knowledge for a used car.