The Bottom Line Carrier coverage maps are only a starting point; check with friends or neighbors who use the carrier you are considering to find out their experiences. Take full advantage of the trial period offered by most carriers.

Coverage is the foundation of our triangle because it is the most fundamentally important element. No matter how cool your phone looks, it is little more than a paperweight if it doesn't work where you need it. Unfortunately, coverage is also the most difficult element to assess ahead of time, because, like fingerprints and snowflakes, each person's calling patterns are unique.

We think it pays to do a two-step analysis here. First, find out if the carrier generally has a good service reputation in the places you are likely to use your phone — for example, along certain highways on which you commute, or in an office building where you work. You can get a sense for this by asking others who have that carrier what their experience has been and by reviewing the carrier coverage maps. Don't forget to ask others about data speed and reliability if you'll be using your phone for more than voice calls.

More difficult is figuring out if the phone is going to work in places that are unique to you. For example, if you have a home office where you'll need clear and reliable service, the only way you can really know is to try it out.

About Those Coverage Maps Every carrier provides maps that show off the areas where they claim to have service. Some carriers' maps are more detailed than others, and some carriers now offer street-level detail on their websites, but even the best ones only go so far. Do not assume you'll have service just because the map indicates that you will. All carriers have “dead spots” that are rarely shown on these maps. Wireless is an imperfect technology, and your ability to make a call at any given time is going to be affected by such varied elements as weather, topography, system demand, and even where you are in a building.