There are a lot of ways to go here, but if it's inside and you just don't want dust to accumulate on the finish I'd agree with Michael and the tarp...do not go with one of those elasticized 'car covers' as they can easily scratch the paint.
Personally, I like the 'car capsule' which is a heavy duty vinyl that is inflated and encapsulates your car:
http://carcapsule.com/ This will keep everything off the car and maintain it at a fairly constant temp and humidity.
