Store the battery on a trickle charge, or if you are able, charge it weekly, stored in a relatively warm place.
My buddy in colorado uses an old family sized tent he found for free on craigslist for winter storage. Best case scenario because the bike doesn't touch any part of the tent, and it's (for a 70's tent) hermetically sealed.
Lucky for pretty much everyone else you don't live in SF, where your bike will rust to bits even stored in your garage. I wash and wax frequently, and Keep a layer of "Boeshield T-9" on anything steel that doesn't get hot (bolts and other hardware).
PS, T-9 is awesome. You can buy it at your local bicycle shop. Originally designed for corrosion protection on the landing gear of airplanes, it makes an extremely good rust barrier that dries to a hard wax coating, and is tenacious.