Before You Buy a Cell Phone

Know the Networks

Before you start shopping for a handset, consider your cell phone service. Are you happy with your current carrier or contemplating a switch? Your handset and service options depend on what the cell phone company offers or permits (for example, you can obtain an iPhone only from AT&T; browse to our comprehensive iPhone coverage, and also see our hands-on product review).

Even if you can purchase a handset from a third party, your choices will at least be limited to phones compatible with your mobile operator's network.

The United States hosts two main families of cellular network technology. Sprint and Verizon use CDMA and its faster progeny--1xRTT, EvDO, and EvDO Rev A--nationally; meanwhile, AT&T and T-Mobile work with GSM/GPRS and a speedier upgrade, EDGE, nationally. (See "Net Nomenclature" for details on the various technologies' speeds and brand names.)

Of the two, GSM/GPRS is a little more flexible because all service and subscriber information is stored on a small, removable SIM (Subscriber Identity Module) card. In theory, you can switch carriers simply by replacing one service's SIM card with another's; conversely, you should be able to switch handsets by slipping your current SIM card into a new phone.

In practice, however, a number of GSM carriers--including AT&T and T-Mobile--use software that locks a handset to a specific SIM card. To use a different SIM card, you must unlock your handset--a process that usually involves entering a code that you obtain from your carrier.

In some cases, a GSM carrier will help you unlock your phone if you have been a subscriber for a certain period of time. For instance, T-Mobile users can unlock their phone after 90 days, though the company says that an unlock code isn't available for all cell phones.

Some mom-and-pop cell phone shops and Web services will unlock certain GSM phones for a fee. Another option is to buy an unlock code from sites such as Mobile Unlock, TravelInsider.com, and UnlockToTalk--or if you're lucky, you might find an unlock code on a forum by running a search for your particular model: "Nokia 5300 unlock code," say.

Alternatively, you can seek out a new, unlocked handset from a third-party vendor (more about that later).

CDMA phones don't use SIM cards. Rather, they must be activated by the carrier. These handsets usually have firmware that permits activation only by a specific carrier: There's no easy way to reprogram them to work on a different carrier's network.

Network services vary by location. So if, for example, you care about having high-speed data services, you'll want to check out coverage maps for different carriers.

If possible, you should do some reality checks on those maps, perhaps by borrowing a friend's phone. After all, there's no point in purchasing a high-speed handset if the carrier's network doesn't extend to the places where you intend to use it.

Help With Handsets

Once you have selected a carrier or have decided that your choice of handset will determine your carrier, you are ready to start looking at handsets. To get a sense of what's available, read editorial and user reviews, including our Top 10 Cell Phone-PDAs chart and our Cell Phones & PDAs Info Center. For general guidance on features, consult "How to Buy a Cell Phone". Another great resource is PhoneScoop's Phone Finder, an online tool that generates a list of cell phones that match your stated preferences.