After that, you might want to check the refrigerant level when you go to restart it later. That might need a refill.
If the car is periodically started and driven around to give it some exercise, be sure to run the A/C each time it is driven. This helps move the refrigerant's oil around in the system and keeps the compressor shaft seals moist so they don't dry out and leak, causing a loss of refrigerant. One of the best ways to keep an A/C system working properly is to regularly use it, even in winter (defrost works better with A/C). Non-use will kill an A/C system over time.
Other things to do:
- Make sure the windshield washer fluid can handle the cold temps (typically can handle down to -25F) so that the fluid jug doesn't freeze. I recently was in below freezing temps with summer Rain-X washer fluid (only good to +30F, i.e., 2 degrees below freezing). It made slush on the windshield when I used it. I promptly ran it out of the system and refilled it with the winter (-25F) stuff.
- It's probably a good idea to check all fluid levels and top off as necessary.
- Inflate tires to max rated PSI on tire (~ 44 PSI?). They'll lose some air during long-term storage but the pressure will be close to where you want them to be after storage. I typically run 40PSI in my tires rated at 44PSI max.
- Fully top off the tank to the brim, with liquid at the top. Wait patiently for all foam to settle. Hopefully wherever you fuel up is close to where the car will be parked and you won't have to drive far after filling it.
- Dump your favorite fuel additive into the tank when you fuel it up. OK to give it a bit of an overdose of additives. Use an additive that does something to control water.
- Make sure the brake rotors are totally DRY when you park it. Lightly and briefly 'riding' the brakes right before you park it will help dry them off. Light and powdery surface rust from moisture can form on the rotors after sitting parked for even as little as a few days.
- Like others said, hook up a trickle charger to the battery to maintain it and keep it ready to go.
I'll soon be parking my 05 PD Jetta Wagen for the winter to keep the road salt off it and keep it in pristine showroom condition. It only has 7800 miles on it (and NO, I'm NOT selling it!). My 02 Golf (w/185k miles!) remains as my daily driver. If another driver is going to slide into me during a snowstorm, I don't want it to be the Wagen that gets hit. I'll be starting and running the Wagen about once every 1-2 weeks so that it doesn't atrophy from non-use. I'll drive it and give it some use on the good weather days. The Wagen is my 'baby' to have last well past 2007 in case TDIs get legislated out of existence due to tightening Tier 2 emissions regs.
Like others have said, the list of things you can do prep it for winter storage is endless. You be the judge. Probably the number one thing to do is fully top off the tank all the way to liquid at the top (no foam) and use a fuel additive that does something to control water.