Hrm. Really, hand washing would be the best. But, if you can't do it during the winter, once every few weeks of a automatic car wash (I'm sure where you live there are the "touchless" types without spinning brushes, this is the only type I would consider going to, even though I don't normally take my cars to any of them). Personally, I think a clean car, albeit with some swirling (these places are known for causing this over time) is better than a car that has salt caked on it. Your car isn't going to be perfect, you don't have the means. If it was in a showroom all day, great. But, enjoy it. You can handwash at those booths when it warms up (I live in NY, it gets above freezing sometimes long enough to wash the cars at these booths, take advantage of it).

A major thing would be to get a synthetic polymer wax on it. Screw the regular old carnaubas in winter, they just don't last long enough. A well wax car is much easier to clean than a car with no wax. Go to Autopia.org and read around. Some names of good, known synthetics are Klasse, Zaino, Blackfire and Platinum. I have to go, but any questions I'll answer when I get back.