Here's some tips to would-be FaceTimers:
First, make sure FaceTime is enabled. Tap 'settings' on your new iPhone, scroll down to the green icon called 'Phone' and select it. The second item down is labeled FaceTime. Make sure it is turned on. It may take a moment for FaceTime to become active so make sure you get a confirmation.
Now when you call someone you'll see an on-screen FaceTime icon. You can tap it, and the other person, assuming they are on Wi-Fi and have an iPhone 4, will get an invitation. If he or she accepts you'll be chatting in just a few seconds.
A couple of other things to think about. Holding the phone at arms length for any period of time might not be fun. You should consider having a way to rest your arm while you are chatting away. If you are tired of displaying your ugly mug you can tap the camera icon at the lower right of the screen and you'll activate the camera on the back of your phone so you can tour your garden or show your latest tech gear off. To switch back to the forward facing phone, tap the icon again. Natch.
Finally, what if you don't know anyone with a new iPhone and want to test it? Apple comes to the rescue here. You can call 1-888-FACETIME (1-888-322-38463) and you'll be able to chat with an Apple Rep from 8AM to 8PM CDT. Yes, you'll note an extra digit in the number. Trust me, it works.