Does the iPhone have a SIM card? How do you remove the SIM card from the iPhone?

Of course, all iPhone models use SIM cards. It is not clear why many people think otherwise. Specifically, the original iPhone, iPhone 3G and iPhone 3GS use a Mini SIM, more typically called just a SIM card, and the iPhone 4 uses a Micro SIM. The difference between these standards largely is size.

The SIM card in all iPhone models can be removed with an unfolded paper clip or a SIM eject tool, as shown below:

Photo Credit: MacLife Magazine (Original iPhone)

It also is worth noting that the hole to push out the SIM card is on the bottom of the original iPhone, iPhone 3G, and iPhone 3GS and is on the right hand side in the middle of the device for the iPhone 4.

When combined with "unlocking" software, switching SIM cards makes it possible to use the iPhone on carriers other than the pre-determined one from the country of purchase.

How can I begin to troubleshoot a problem with the iPhone?

In the Apple Support Site, the company offers a helpful troubleshooting "engine" to walk you through basic problems with freezing, calls and connections, synchronization and recognition, e-mail issues, and more.

How can I upgrade from an older iPhone to a new iPhone?

Apple has posted a useful support document that covers upgrading from an older iPhone model to a new one. This document provides step-by-step instructions to backup your older iPhone and restore the backup to the new model, which allows one to seamlessly migrate "saved SMS messages, email accounts, photos, notes, and other personal settings".