For the average consumer, choosing a cell phone often comes down to cosmetics and personal preferences: size, color, ease of use, and ring-tone selection. For the small-business customer, however, choosing the right cell phone should always be a matter of substance over style.

Many customers start with a service provider, then choose from the available phones, in part so that they don't need to switch phone numbers. That will soon change, thanks to number portability. Starting November 24, the Federal Communications Commission will require all carriers to let customers take their numbers with them. This is good for consumers in general, but it's essential for small-business customers because their phone numbers are part of their identities.

Since you're no longer locked in to a particular provider, you can choose the right phone based strictly on design, features, and service. Here are some of the key features to look for.

The basics
Long battery life is essential. Look for phones that use a lithium-ion (li-ion) battery rather than a nickel-metal-hydride (NiMH) one. Li-ion batteries weigh less and provide 10 to 20 percent better performance than their NiMH counterparts. You'll want a phone with a rated talk time of at least three and a half hours, preferably closer to five hours. If your mobile comes with a desktop charger, splurge for the travel charger since it's significantly smaller and easier to pack for business trips.

If your travels often take you well beyond your home calling area, make sure your phone supports analog roaming. Although analog calls are expensive, you'll be guaranteed coverage even in remote rural areas. If your travels take you overseas, you'll want a GSM (Global System for Mobile communications) phone, which operates on networks (GSM 800/1800/1900) in Europe, Asia, and the United States.

You'll also want a handset that features a hefty address book--at least 300 names with support for multiple entries per contact. Some phones allow you to include information such as e-mail, Web, and street addresses with your contacts. You can enter all that information one key at a time, or you can get a phone with the ability to sync with Microsoft Outlook on your PC. Also making inroads in this area is SyncML, an open standard that establishes a common language for synchronizing information between mobile devices and other computing equipment.

More-advanced features
Among other features, check to make sure the phone you want supports conference calling, just in case you have to conduct an emergency meeting while you're on the road. You'll also be hearing a lot more about two-way, walkie-talkie-style communication in the near future. This technology was pioneered by Nextel. The company's Group Connect service lets you establish 200 groups with up to 25 members in each group--a good option for instantly reaching your employees or coworkers. Verizon Wireless recently announced its own service, called Push To Talk, and Sprint PCS is expected to announce a similar service later this year.

Because you never know if you'll need Internet access in a pinch, it's a good idea to purchase a phone that can connect to your laptop as a modem. You'll need to invest in the proper software and cables and make sure that your notebook can support such a connection. Or you can skip the wires altogether and get a Bluetooth-enabled cell phone. If your PC or PDA doesn't feature integrated Bluetooth support, you can purchase an adapter to add this functionality. Then you can browse the Internet using your phone as a wireless modem; you can also use Bluetooth to sync phone numbers and addresses between your phone and other devices.

Even better, skip your notebook altogether. Fast Internet access is rapidly becoming a common feature in cell phones. Most GSM phones support GPRS (General Packet Radio Service) networks, which offer always-on Internet content and data services, enabling access to Web browsing, e-mail, and multimedia content. For phones that use the CDMA platform, 1xRTT (single-carrier radio transmission technology) typically provides data services twice as fast as those of GPRS. On the horizon is a technology called EDGE (Enhanced Data GSM Environment), designed to provide data transfer over existing GSM networks up to three times faster than GPRS.

Get smart
If you spend most of your time away from the office meeting with clients, you may want to consider a smart phone, which combines cell phone and PDA functions in one unit. These phones are larger and much more expensive than standard handsets, often costing as much as $600, but they eliminate the need for two separate devices. Smart phones are available in Pocket PC, Palm, Symbian, and BlackBerry platforms.

Christopher Null is a freelance business and technology journalist in San Francisco. He has written for Wired, Smart Business, PC World, and Business 2.0.  He is also a veteran of numerous small businesses--including his own Internet start-up, filmcritic.com, which he has operated since 1995.