Whoever came up with the idea of consolidating the car rental companies in a single location, thus enabling you to just hop on a single shuttle instead of hunting down your car rental company among the throngs of buses is simply a genius. It is such a simple idea, but after you have been up all night on a plane and have no mental capacity to think, looking for a single shuttle bus labeled "Car Rental" is much welcomed relief.
When you land at McCarran, simply look for the signs labeled "Rent-A-Car" and head on out the doors into the desert heat (or cold, depending on the time of year) and make your way to one of the blue and white (at least I think it was) shuttles which will whisk you to the facility. Once there, find your rental company and its a cinch to get your car and be on your way...depending on your company of course!
Returning, just follow the signs from the highway to the rental car center and once inside the cavernous garage, follow the signs to your car rental company (Avis and Budget are the first ones). Take care of the paperwork and then board the shuttle back to the terminal and back on your way home!
Like I said..it's pretty darn easy! Although, I don't particularly care for that surcharge that is paying for it...oh well, can't get everything I suppose!