Be sure that you care for that beautiful fir tree, even before you get it into your home. Try to keep the tree covered with some type of tarp while you're transporting it (especially if it's strapped to the top of your vehicle) or it may dry out. You may want to ask the grower or the person who runs the lot if they can provide you with a plastic bag for the tree, many of them provide this type of thing.
If you plan on leaving the tree outside for several days before being lugging it into the house, keep it out of extreme heat of cold and keep it away from the wind. It's a good idea to place it under or behind something—but don't squish it. Additionally, if you plan on storing your tree for a few days, it's smart to put the trunk in water to keep it from drying out.