I bought all new tires. Here are my tips to making your experience as good as possible:
First -- use the Discount Tire website to figure out which tires you need. Enter your car information and it gives options with prices and recommendations.
Second -- reserve the tires you want online and schedule an appointment online with your preferred store.
Third -- decide whether or not you want the 'Repair/Refund/Replacement' option which they usually try to sell you on at the store.
Finally -- finish your order online.
I arrived on time for an 8AM appointment and was immediately greeted. They looked at my order, took my keys and my car went straight into the bay. 30 minutes later I was driving off their parking lot with all new tires.