There’s no sense in denying it: For most of us, mobile phones are at the center of our universe. The typical feature set of these things is astounding. It’s your phone, your messaging device, your on-the-go Web browser, your camera, your music player, your GPS navigation unit, and more.

If you thought choosing a cell phone was difficult before, it’s even tougher today. That’s a good thing, though, because it demonstrates how innovation in the wireless industry has skyrocketed. We’re seeing rapid progress across all fronts, including displays, data networks, user interfaces, voice quality, third-party apps, and even mobile gaming.

All four major U.S. carriers now offer 4G LTE networks, which are typically 10 to 15 times faster than 3G. The latest crop of Android smartphones is more diverse and powerful than ever. Android is also far and away the sales leader in the U.S. when it comes to smartphones, a result few could have predicted just three years ago. Samsung’s powerful Galaxy S5 is available on every major carrier, while Apple’siPhone 6 is becoming available across the board as well.

Pit against this backdrop, it’s no wonder standard feature phones (handsets without app-based ecosystems) are fading in importance, and that sales are continuing to trend downward.

Taken together, these massive changes make much of the old advice about choosing a phone obsolete. So let’s throw it all away and start over. The topic has become so important, and involves so many decisions, that we scrapped our existing cell phone and smartphone buying guides in favor of a single comprehensive story—the one you’re reading right now.

So what should you be looking for when buying a cell phone? Here are some key points to consider:

First, Choose a Carrier

Despite all the recent hardware and mobile software innovation, your wireless service provider remains your most important decision. No matter which device you buy, it’s a doorstop unless you have solid wireless coverage. Maybe you have friends and family on the same carrier that you talk to for free, and you don’t want that to change with your next phone. Maybe you’re lusting after a certain device—say, an LTE-capable Android phone, or an unlocked smartphone for international travel. And of course, you want to choose a carrier that offers fair prices, and provides the best coverage in your area. These are all good reasons to put the carrier decision first.We have two major features to help you choose a carrier. For ourReaders’ Choice Awards, PCMag readers told us which carrier they prefer based on coverage, call quality, device selection, and other factors. And for our Fastest Mobile Networks feature, we sent drivers to 30 U.S. cities to scope out which smartphone carriers have the best data coverage. Because each of the national carriers sells a wide variety of phones, choosing your service provider should be your first move. Here’s a quick rundown of what each one offers:

AT&T boasts nationwide coverage and a terrific selection of phones, particularly for texting. It has dramatically improved its service quality in the Northeast over the past two years, and is busy building out its LTE network. It’s also the worst-rated carrier by our readers.

Sprint is relatively inexpensive, and offers some media services and a solid high-speed network. It also has the most open approach to third-party apps, letting its subscribers add a wide range of Java applications to its feature phones, although this is becoming less important as smartphones take over the majority of sales. Sprint has two prepaid brands, Virgin Mobile and Boost Mobile, that sell phones without contracts.

T-Mobile offers mostly cutting-edge phones at relatively low monthly rates and enjoys a reputation for good customer service. It’s the only carrier that lets you buy phones with subsidized costs from month to month, without forcing you to keep paying extra once the two years are up. But its network can be weaker than the other major carriers’ in suburban and rural areas. T-Mobile is building out 4G LTE in earnest, and also completed its MetroPCS acquisition last year.

Verizon Wireless is famed for its top-notch network quality and good customer service. Its prices can be higher than the competition, but when it comes to voice quality, Verizon phones often excel. That makes Verizon a perpetual leader in our Readers’ Choice Awards, and it won Fastest Mobile Networks this year as well. Verizon also currently has the largest 4G LTE network in the U.S.

There are also smaller, regional carriers. U.S. Cellular is only available in about half the country, yet it consistently gets great scores on our Readers’ Choice Awards because of its strong commitment to customer service. Finally, you may also see unlocked phones on the market that work with GSM networks such as AT&T and T-Mobile, but that carriers don’t sell directly. These handsets are often imports. Because they’re generally more expensive than carrier-approved-and-subsidized phones, few are sold in the U.S. Our current favorite unlocked smartphone is the Google Nexus 5.