Today, while listening to the radio, an advertisement came on that asked, when shopping for a new cell phone, whether you should shop by phone or carrier first (I didn't even realize the the word "carrier" had entered the common American lexicon). Just when I was getting ready to blurt out my answer (Carrier!!!!), the ad answered the question with another question.... How about someone you trust like Radio Shack? Oy. The first someone you should trust is you. That's right. You. Particularly when you know how to shop for a phone. The answer is you always shop by carrier first. As I have often written, much the same way the three most important things to the success of a restaurant are location, location, and location, the three most important things to consider when buying a new phone are coverage, coverage, and coverage.
The rule is pretty simple: I don't care how beautiful or feature rich your phone is. At any given point in time, your phone is only as good as the network connection it has. If you can't get a reliable connection to your network (or any network for that matter) in the places you frequent most (including your home), the phone isn't going to be of much good to you since most of its important features don't work without a connection. Ignore the coverage maps. Chances are, you have enough friends who have phones from the four major wireless carriers (Sprint-Nextel, Cingular, Verizon Wireless, and T-Mobile). Ask them if you can borrow their phones for a day. Then, try-out the phones in all the places you go including your house. Take the phones along whatever route you use to get to work. Take them along your favorite bike ride or walk. Chances are, one carrier will rise to the top as the one that has the best signal in the most places you go. If you go to Europe, stick to the Europe-compatible carriers with GSM heritage (vs. CDMA) such as Cingular and T-Mobile.
Then, once you've picked a carrier, then check out what phones that carrier has to offer and figure out which one best matches your needs and your budget. Also, check out the specific absorbtion ratings (SAR) of the phones your considering. Sometimes, this is hard to find. But, before any phone is allowed on the American market, its SAR rating must be registered with the FCC. The phone manufacturers and carriers would rather you not look at this number. It refers to the the amount of radiation your human tissue will absorb as a result of using the phone (or just letting it hang on your belt) and some people believe there's a correlation to the risk of cancer. The most honest assessment of the situation is that the jury is still out. While there are plenty of studies to suggest that there's no risk, there are enough other studies that suggest that no one can definitively say "there's no risk" just yet. So, if you're like me, and you need a cell phone but want to take the conservative view of the cancer issue, take the SAR ratings of the phones on your short list into consideration before finalizing the decision. Lower is better. Here at CNET, we run a SAR rating lookup service where most but not all phones (especially the newest ones) can found. In a post that I did a while ago (about the cell phone radiation issue), I give some links and details on how to find phones in the FCC's online database. It's not easy, but all of the ones on the US market should be there.
Need a data connection as well as voice connections? The CDMA-EVDO carriers (Sprint and Verizon Wireless) are the fastest. Today. But, you'll need to sacrafice that speed if you want to use your handset in Europe where handsets provisioned by Sprint and Verizon generally don't work.
Once you've decided on a unit, shop around. For example, if you look hard enough, you might be able to find the same phone from the same carrier for less price at one retailer (including the online retailers like Amazon) than you might another. Then, once you've found the carrier, the right phone, and the right price (and picked the most appropriate monthly plan), do the deal and be sure to opt for the extra $2.50 or whatever it is for insurance in case the phone breaks. I've had to take advantage of my phone insurance multiple times and believe me, it's worth it.
So, in answer to Radio Shack's question, I agree that you'll want to trust your retailer. But it's hardly the first thing to think about when buying a handset. In fact, it's practically the last.