Fill the gas tank to reduce condensation; add fuel stabilizer and run the engine for a few minutes to get the stabilizer through the fuel system; pump up the tires to keep the sidewalls from cracking and prevent flat spots; wash and wax the car; maybe rodent repellent inside or underneath; put a cover on.
Drink beer for the next few months, and resist going out to your garage and starting the car once in a while, while sitting in it pretending it is summer.
Those are the basics from my perspective.
