Even if you're already following the manufacturer's suggested maintenance schedule for your vehicle, it's a good idea to go for a tune-up before winter comes. Finding yourself broken down by the side of the road is always a bad situation, but it's even worse when it's freezing outside. That's why it's worth spending the money to get your car some basic maintenance. You can do some of it yourself, of course, if you're so inclined. But if you're not a car person, take your car to your local mechanic.
Start out with checking your car's fluids -- oil, transmission, coolant/antifreeze and brake. If it's already time for an oil change, your mechanic will typically go ahead and check the others, topping them off or draining and replacing them as necessary. Other things to check include your exhaust system, lights and hazards. If your windshield wipers look ragged or aren't clearing water well from your windshield, have them replaced or buy new ones and replace them on your own. Finally, make sure that your defogger/defroster and heater are operating normally.
There's another important part of your car that needs attention before you set off in foul weather: your tires.