Check the battery and cables and replace if the battery charge is too low or the cables are worn. Winterize the wiper fluid and clean any clogged hoses or nozzles. If it's been a while since your last tune-up, then now would be a good time to replace the distributor cap, points, condenser, as well as the spark plugs, spark plug cables and the ignition coil. While under the hood, check all hoses and belts and replace if they show wear or cracks.
If you're not mechanically inclined, then make sure you take your car to a qualified mechanic. This is especially important if you live in a climate with harsh winters. There is nothing worse than having your vehicle breakdown in the midst of a snow storm due to a failure to prepare your car for winter.
Winter or not, you should have an emergency car kit in your vehicle. This emergency bag should contain items necessary for 72-hour survival for one person, including water, food, an emergency first aid kit, as well as a few basic tools.
For winter the car emergency kit should also include a blanket, flares, pocket hand warmers, jumper cables and a flash light. A folding shovel and a bag of kitty litter can also come in handy in case you get stuck in snow.
When you prepare your car for winter you will also want to keep in mind the necessity of keeping the car full of gas. In harsh winter weather, a full tank of gas can mean the difference between inconvenience and tragedy.