Keep a full tank of gas to prevent condensation. I don't think letting it run in the garage for twenty minutes is a great idea unless there is no way you can drive it due to snow or ice. Also, leaving it sit in one spot and never turning the tires could mess up your tires. I try to take mine out every couple weeks in the winter when the roads are clear and run it for 30 minutes or so. If that's not possible a battery tender would keep the battery from losing its charge, but I suppose you would need to find a way to get it to the trunk.
