The best way is to take the battery out of the vehicle and clean the outside of the battery and terminals. Check the water level before charging. Place the battery inside (heated is best but not necessary) a building or garage.
Batteries will freeze if they loose their charge.
Do not place on concrete floors. Place on block of wood, or plastic tub. Use a battery "tender" or "maintenance" charger.
If you use a trickle charger or any other type of charger, charge it until fully charged and remove it completely. Check water level and recharge monthly.
I have work vehicles and tractors that do not get much use. I leave them on a battery tender year around and check the water level periodically, and clean the terminals when needed. This seems to work pretty good for me in South Dakota climates.
I have bought battery "tenders" fro Harbor frieght for as little a $7 and used them with good luck.
1. Always check water levels before charging. Low water levels when charging will burn it up.
2. Use a battery "tender" for long periods over two to three days. Not a trickle charger.
3. Check on the battery periodically whenever using a charger.
4. A battery should never be warm to the touch or hot when on a "tender". A battery should never be hot to the touch.
5. Wear safety glasses and NEVER create a spark or have an open flame when charging batteries. See the following link:
http://www.stovebolt.com/techtips/battery101.html
