Just the lights, mirrors, windows and windshield. The other stuff will blow off. As the first rule of Italian driving says..."what behind me....no matter!"
So that's where I get that attitude from....
When I get caught in a snowstorm, step one is to knock any loose snow surrounding/on the driver's door off so it doesn't end up inside the car. Then I start the car and turn on both defrosters. Then I pull up on the parking brake if it is not already set. I follow this up with knocking loose snow off the hood and lights. By this point, the defrosters have melted enough that the windows are easy. I clear enough off the trunk to be able to use the rear window.
As for shoveling, I always only shoveled enough to get the car out without high-centering the damned thing. I also learned when driving a front wheel drive car in snow, back into parking spots. Makes it a hell of a lot easier to get out again.