The parking lots are just large open fields with few fences to restrict your movements. All of the halls are within a circle about 2000' wide. Walking slowly through the halls makes your joints stiff, so walking briskly back to the car to hide your stash is the way to loosen up the old knees. Exercise is good for you.
A few other hints: If you see something you really want, either buy it, put a deposit down on it, or at least make a note as to what building and aisle it's in. It will not be there when you get back to that hall again a few hours later.
Bring multiple plastic grocery bags, plenty of cash (there's an ATM in the parking lot) and a list of what you're looking for. Your senses will be overwhelmed by the whole scene, and confusion can happen. (And I am not necessarily talking about the crop dusting).
If it's sunny out, don't drink the lemonade. Don't ask me how I know.
The UPS company generally has a presence in one of the halls to allow large items to be shipped home, if there's limited room in your car. Turn off your headlights when you arrive. Bring an extra set of car keys. Try the homemade french fries with vinegar. Yum.