Winter won't rust your car- road salt will.
Prep it by filling up with 100% gasoline- none of that 10% ethanol stuff...check
www.pure-gas.org for a location near you (you don't have a location listed).
Wash and wax it real well.
Know that a car cover CAN ruin the finish. If there is any dirt in there, a car cover flapping about can act as sandpaper....
Lube the hinges, "over wax" the car and change all fluids.
My 1991 Nissan was bought new by my buddy Chris here in Chicago in August of 1991. I was his ride to the dealer for him to pick it up. Two months later he moved to Seattle (no road salt) to get married and open a dental practice. 19 years later (in 2010), he gives me his rust-free car with 98,000 miles on her. All records since new- including the window sticker. Black car....
I don't have a garage right now- so every winter, I store it properly and start it up once a week, charge the battery, over wax the body, change fluids, and move it a few feet to keep from flat spotting the tires. I've done this for 5 years....no problems.
After new fuel injectors a couple weeks ago (thanks to advice from members like PapaSmurf here), she idles and runs like new. No rust.
Conclusion: Clean it like it has never been cleaned, and wax it- not for showroom shine, but real thick for protection. And use real gas so nothing gets gummed up. Good luck new owner!