Thinking of joining the wireless multitudes? More than 69 million people subscribe to cellular phone services in the United States, and more are signing up all the time. And Washington is cellular city, with cell phones pressed to ears on every sidewalk and--for better or for worse--in seemingly every car. It's easy to see why--wireless phone subscriptions can be had for less than $20 a month.

But do you really need to join the crowd? Before you buy, consider a few points. How much use would you get out of yet another telephone, when you're already connected at home and at work? Do you absolutely have to have a phone handy at every moment of the day? If your daily commute is short, you might save a lot of money by carrying around change for pay phones--that mere $20 a month translates into a minimum of $240 a year, and almost certainly more than that--and, if you need to be reachable on the cheap, a beeper.

But let's say you have decided to buy. The number of questions you have to ask yourself expands. Are your calls likely to be local, or long-distance? Do you generally stick around town, or are you often on the road? Answering those questions will help you determine whether you want a less expensive local plan or one of the big nationwide plans.

Once you begin thinking phone-ly, you'll have to decide which company to go with. The Washington area has six (check chart for update) choices: AT&T's Digital PCS, Bell Atlantic Mobile's digital and analog services, Cellular One's digital and analog services, Nextel's business-oriented digital network, and Sprint PCS. (Another option, Sprint Spectrum, is being discontinued by Sprint, and its customers are being moved to the PCS network.) The accompanying chart lays out rates, estimates of costs under various calling patterns and the impressions of our reviewers; the maps at right list coverage areas of the digital services.

The cheapest plan is rarely the least expensive. For one thing, unless you have the self-control of a monk, you'll always use more minutes than you originally sign up for. Cheap plans get you a subscription, but the higher-priced extra minutes rapidly ratchet up the costs. If you already pay for a lot of long-distance calls, you can probably save money with the national one-rate programs at the high end of the price scale, which kick in plenty of free minutes. The industry, you see, is after the most lucrative customers--the folks who will use the most phone time and extra services. That means the biggest savings are at the high end of the price range; paradoxically, the more you spend the more you'll save.

You also need to consider the kinds of options you need to make yourself truly wired--well, unwired, but you get the idea. Digital services usually offer voice mail and paging as part of the package. Some plans also offer two phones on a single plan--an option that can be invaluable for a husband and wife coordinating the logistics of getting kids to soccer, ballet and karate practice on those exhausting weekends. For pure convenience, it's hard to beat prepaid phone plans, which have grown from a $300 million business to more than $3 billion in just five years, according to industry figures.

The latest new option, though, could be the most important yet: Internet access directly from your phone. Sprint PCS, for example, this month kicked off a service that brings a small-scale version of the online world to the tiny screens on the latest phones. Users can check news headlines, use e-mail, get directions from the online site MapQuest and more, with the option starting at $10 a month more than regular service.

Once you get the phone, you'll probably want to use it everywhere. Don't. Think about how those callers used to irritate you at the restaurant, in the movies, and everywhere else. A little consideration goes a long way. And as for talking and driving, well, that's a no-no too. Cellular use has not been proved more of a hazard than any of the other idiotic things that drivers do that distracts them from the road, but anything that diverts attention from the grave risks of driving should be avoided. Safety experts recommend pulling over to make or complete calls, and they say that drivers should use common sense. As the bumper stickers showing up on cars everywhere suggest, "Hang up and drive."