This is how I got my iPhone 5.
it's very simple, if you go to the site right now the "buy now" button will be grayed out. Once it hits 10:00 PM you just go through the process of picking out your phone like you were ordering it online. Once you have it all picked out, when you check out it will have an option for store pick up. Once you click that, it will show you what stores are available for pick up. If you don't see a store you'd be willing to drive to, you just close out.
One thing to note, the stores available seem to vary throughout the first hour. My fiance for instance got hers at a store that was around 30 minutes away from where we live. Since she got one, I cancelled my pre-order from apple.com and did the same reservation and a store 5 minutes from my house had one available. So keep trying throughouth 10:00 PM - 11:00 PM. If you don't have any luck passed 11:00 PM I'd just try the next day.
Good luck! Love my new 5!
Edit: Just incase you need it, here's the actual link. It's not just the regular apple.com store it's the retail version of the online store.
http://www.apple.com/retail/iphone/