When arriving at the Phoenix Airport, you can take a shuttle to the PhX car rental center. All the shuttles that I have taken in the last year, always have a very nice driver that will help you load and unload your luggage. It takes about 5-10 minutes to arrive at this phx car rental center.
When you arrive, your luggage is unloaded and you enter a huge building full of car rental options. The first time we rented a car in the phoenix area, we did not pre-set up a reservation and chose the car rental place that had the shortest line.
This last visit, my wife decided to book a car in advance. We went with Hertz, which I will save my review for them for another time. ( Just a side note DO NOT GO WITH HERTZ).
Then there are elevators that direct you to the floor where you pick up your rental car through the company you chose, and off you go. Very easy dropping back off he car too. Signs are very helpful..
Shuttle drivers are very helpful, overall a good experience.