To keep your car battery from dying in cold weather be sure to start your car up often and take it around for a drive to keep the battery from going down.
Also I would recommend getting a trickle charger that connects to the cars battery permanently and then you plug the trickle charger into the electrical outlet of your home.
The trickle charger will keep the battery charged up so that it won't go dead or go low of charge when the car is sitting overnight or while you're at work etc.
I always plug my trickle charger into my outlet at home when it's really cold and so far the batteries have stayed up.
The cold weather causes the chemical reaction to slow down in the battery which then makes it lose it's charge and loses it's ability to properly crank the engine over.
Be sure to keep some Jumper Cables in your car or one of those Portable Jump Starters such as a Halo Jump Starter in case you need to jump start your vehicle yourself.
Make sure the battery terminals are also clean of corrosion and tight and if they are corroded you can use some baking soda and water to clean the battery corrosion off.
Then use a hose to wash the corrosion and baking soda off.