I thought it was email-only. The guy at my local Apple Store took my name and email address along with which model I wanted. I wish I could do this for the launch as I was told by a Genius that they stopped reserves, but I don't know. I received an email stating that I'll receive another email when they get my iPhone.
I hope one is reserved for me in the next shipment or this is a bad system since I could just keep calling them if they're saving some for walk-ins when they get deliveries and I could receive it sooner.