These are some of the fastest phones around. James Martin/CNET

"Which phone should I buy?" This is the single most common question readers like you ask phone reviewers like us every day. We get it, it can be a challenge, especially with superb choices such as the Samsung Galaxy Note 4 and iPhone 6 Plus battling it out against the Sony Xperia Z3 and second-edition Motorola Moto X. But depending on your price range and what's available where you live, the new phone you should be getting may not be a flagship -- it could turn out to be the Nokia Lumia 635 or one of the Motorola Moto Gs.

On the bright side, options are a good thing, so long as you're armed with the knowledge necessary to make smart shopping decisions. Sit tight as we lay out what you need to know to find the best new device for you.

For more top smartphone picks, check out CNET's list of our favorite phones.


Three key phone-shopping essentials

1. Don't be a cell phone cheapskate

Contract or no contract, chances are high that once you commit to a new phone, you'll hang onto it for a while. Therefore, buy the best device you can afford. You'll need the camera quality and processor to last you as long as possible until your next upgrade. The battery, too, becomes less efficient at holding a charge as your phone ages, so you'll want to choose one with a high capacity.

An added benefit of going for a high-end handset, say like an iPhone 6 or Samsung Galaxy S5, is that the resale value tends to hold over time, so make your device an investment that pays off.

Read: How to sell your phone for cash


Premium handsets cost a bundle, but will age with grace. James Martin/CNET

2. Know which phone features you want

If you understand exactly which features and capabilities you'd like to see in your new phone, it'll help you avoid paying too much for those you don't want or need. Some, like the Samsung Galaxy Note Edge, have it all -- including a curved screen with its own interface and navigation controls. Yet if you'll never use the stylus or the new UI, you'll be overspending for a pricey novelty device.

3. Find the right design

Buying a cell phone means entering into a deeply personal relationship with a highly portable physical object. That's why you should think hard about how it's designed, since you and it will be spending plenty of quality time together. Make sure you're comfortable with the way it looks and -- this is important -- feels in your hand, and make sure that your phone-to-be reflects your personal sense of style. This is as true for sleek metal handsets and simple flip phones as it is for rubber-plated rugged handsets.

A thick, rugged handset like the Kyocera DuraForce won't do you any good if you don't enjoy toting it around. Josh Miller/CNET


Cell phone types

Smartphones
At the top of today's handset pecking order is the smartphone. These devices typically have the most power, and top-notch components: the fastest processors and Wi-Fi; the highest image resolution and memory capacity and the most pixel-rich screens. By definition, they run true mobile operating systems; think iOS and Android, but also Windows Phone and BlackBerry OS. They also support downloadable applications through virtual storefronts that are tied to their associated software platforms, like the Google Play store. Because of all their capabilities, smartphones are usually the most expensive phones on the market.

Messaging or feature phones
One step below smartphones, feature phones strive to offer many of the same capabilities as smartphones. Instead of popular mobile operating systems, these gadgets run proprietary software crafted by their manufacturers, such as Samsung or LG. Many feature phones are made primarily for text messaging and e-mail, though you won't be required to buy a data plan. Several of these designs sport full QWERTY physical keyboards. With a raft of cheap, available Android and Windows Phone devices, feature phones are fewer and farther between.

Basic phones
There are plenty of people who have no interest in viewing full desktop-quality Web pages or running apps on a mobile device. Simply put, they just want a new phone for making calls, and that's it. No funny stuff. Basic handsets are uncomplicated use traditional simple keypads. They typically come in clamshell designs that flip open, or in tall, narrow candy bar form. They're typically lighter and smaller than feature phones and smartphones.

The BlackBerry Passport is a rare modern device to have both a classic QWERTY keyboard and a smartphone OS. Josh Miller/CNET


Key consideration points

Screen size

Large screens (5 inches or greater)
Smartphones are getting bigger, that part is undeniable. A 5-inch screen (measured diagonally) used to be considered massive, but on today's sliding scale, that's at about the bottom of the Big Phones bucket. Even Apple has gotten into the "phablet" game with the 5.5-inch iPhone 6 Plus. A 6.4-inch device is the largest we've seen, but most people consider the 6-inch Google Nexus 6 and Nokia Lumia 1520 to be about as large as they'd really want to palm.

Medium screens (4.5-4.9 inches)
Phones in this middle category are more portable, but also tend to be more midrange, like the 4.5-inch HTC One Mini 2. One benefit: phone owners can grip with one hand while their thumbs comfortably reach all portions of the display.

Small screens (under 4.5 inches)
Thanks to the increasing number of gargantuan smartphones hitting store shelves, compact cell phones are a shrinking segment of the mobile handset market. That said, some people still place portability highest on their list of phone features. Unfortunately, options are slim. Most phones in this size category are entry-level smartphones or feature phones with low screen resolutions, like the straightforward 3.2-inch Pantech Vybe.

For more on specific display technologies, check out the "deeper dive" section at the end of this guide.

Processor

The beating heart of any phone is its processor, or CPU. It provides the computing power to churn through various tasks, like opening and running applications. A fast processor also has a big impact on overall performance, such as how smoothly a phone handles flipping through menus and running home screens.

Traditionally, clock speed, listed in gigahertz, has been the quick way to judge CPU power. These days a chip's architecture, specifically how many computing cores it has, is becoming a more reliable predictor. Another factor is that older processors tend to use less efficient designs, making them worse performers while being harder on batteries than their newer counterparts. We talk more about processors below.

Camera

A phone's camera quality depends on a whole host of variables. More megapixels will always sound better on a fact sheet, but we know some good 8-megapixel cameras that take better photos than a bad 13-megapixel shooter. (Read on and see the bottom section for more details.)

Also important are the lens quality, which could aid the sensor by exposing it to more light. The sensor itself might also offer a lower pixel count, but be more sensitive to illumination, resulting in better performance in low-light conditions.

Many phones -- such as those from HTC and Microsoft (formerly Nokia) -- ship with fancy image processors that promise high image quality, plus the horsepower to drive the camera and autofocusing systems faster. The end result is nimble shot-to-shot times with minimal shutter lag.

Apple's iSight camera improves year after year, though its megapixels remain at 8. The iPhone 6 Plus has optical image stabilization besides. CNET

Optical image stabilization is becoming increasingly important for phones, too. Samsung's Galaxy Note 4 and the iPhone 6 Plus are two that include the physical component for steadier, clearer photos.

With the rise of social network sharing, front-facing cameras are more important than ever before. In addition to seeing higher-resolution topside cameras, vendors are also concentrating on more software dedicated to the art of selfies. The HTC Desire Eye and Sony Xperia C3 even come with a flash.

Read: Best smartphones for selfies

Battery

If your cell phone battery conks out, all the snazzy features in the world won't be able to help you. Manufacturers have begun to recognize the critical importance of battery life and are squeezing greater-capacity batteries into their phones. Typical phone batteries start in the neighborhood of 1,700mAh and go all the way up to 3,500mAh.

Manufacturers list battery performance in terms of talk time, standby time, or how many hours you can expect a device to perform tasks such as playing video and music.

Wireless carriers

Choosing a wireless carrier is a less difficult prospect than it used to be, with more phones sold across carriers and the higher prevalence of contract and contract-free options. Still, it requires a lot of time and math to puzzle out exactly which operator offers you the best deal. It's worth the time.

That said, when selecting a carrier, first on your list of criteria should be coverage. You'll want a carrier with decent coverage in your home and at work, and all the places in between. For more about carriers and networks, see the next section.

Figure out if you'll be sticking to urban centers or trekking through rural areas often. Perhaps you won't even leave your home neighborhood much or, conversely, you plan on doing plenty of international trips. With your wireless usage in mind, settle on a carrier that offers broad coverage. Alternatively, you may be satisfied with a regional carrier that covers a limited area.


Feature deeper dives

Want to know more about some of the features mentioned above? Read on for a deeper analysis.

Mobile networks and 4G data

The wireless network technology at the backbone of your smartphone is a veritable alphabet soup of acronyms and industry buzzwords, and you could spend an eternity studying how cellular infrastructure is built and works. Here's a basic overview of what you need to know.

CDMA
CDMA stands for code division multiple access, but more importantly it's a method by which cellular radios transmit and receive voice and data. This standard is found mostly in America and to some extent Asian countries such as Japan and Korea. For example, major US carriers that use wireless networks based on CDMA are Verizon and Sprint.

GSM
GSM, aka the Global System for Mobile Communications, first referred to in French as Groupe Special Mobile, is a standard created for use in Europe. GSM then spread to other corners of the world, with carriers operating GSM networks across Asia, the Middle East, and Africa. It's the most widespread. The two technologies are incompatible, so phones locked to CDMA networks won't work in GSM areas, and vice versa.

CNET

HSPA+
Based on the older High-Speed Packet Access, which topped out at 3G speeds, HSPA+ supports a theoretical peak download throughput of 168Mbps. This may sound pretty fast, but in practice the protocol delivers data speeds just marginally faster than 3G, and average download speeds of approximately 3 to 5Mbps. This causes us to think of it as really a 3.5G wireless solution.

4G and LTE
LTE, or Long Term Evolution, is the "new" generation of faster data connectivity for both GSM and CDMA technologies. Often referred to as 4G or 4G LTE, it's the speediest data throughput you can get right now. LTE Advanced, a step beyond LTE (but still part of the same family) gives data speeds still another boost, and is rolling out in bits and pieces. VOLTE, which stands for Voice Over LTE, relays voice service over data channels, allowing you to surf and speak at the same time even if you have a CDMA phone.

Screen technologies

LCD
LCD screens, short for liquid crystal display, have come a long way from the alarm clocks and digital wristwatches of the 1980s. Today's smartphone LCD panels offer HD resolutions of up to 2,560x1,440 pixels. LCDs use of an external backlight for illumination, which often results in more shallow viewing angles and lower contrast compared with AMOLED displays. On the other hand, colors often appear more natural.

Retina Display
Apple uses what it calls Retina Displays in its latest iPhones. This is essentially a clever marketing phrase to say the iPhones (the iPhone 4 and up) sports LCD screens with minimum resolutions of 326 pixels per inch (ppi).

AMOLED screens on this Samsung Galaxy S5 and others typically produce high contrast and vibrant colors. Josh Miller/CNET

AMOLED
Long billed as the screen technology destined to replace LCD, active matrix organic light-emitting diode displays (AMOLED) use organic chemicals as the material that generates light. Much like neon light fixtures and plasma HDTV screens, AMOLED displays use OLEDs to create light when they're exposed to an electric current. Since they don't rely on backlights for illumination, AMOLED screens tend to have higher contrast and more vibrant colors than LCDs. LCDs use liquid crystals that twist shut and block out light from LEDs placed behind them. Samsung is on the forefront of AMOLED panels.

Processors

Qualcomm Snapdragon
The current CPU smartphone king, Qualcomm's Snapdragon family of processors shows up in many Android and Windows phones around the world. Right now, Snapdragon 805 is the chip to beat, but the 810 is right around the corner, promising upgraded power to rival the heady task-processing we see today.

qualcommsnapdragon.jpg

Apple A8
Apple's latest wafer of processing silicon graces the iPhone 6 and 6 Plus with 64-bit mobile phone processing. Apple claims the system is 25 percent faster than the A7. All other details remain officially hush-hush.

Samsung Exynos
As well as displays and memory components, Samsung makes its own processors under the Exynos brand. Its most recently announced Exynos chip, the Exynos 7 Octa, promises 64-bit computing, and will surely turn up in some global variations of the company's top phones, like the future Galaxy S6 and Galaxy Note 5. Other Samsung phones will likely continue to use Qualcomm's chipsets.

Motorola X8
Motorola took a unique approach in its smartphone lineup for 2013. Instead of cramming the fastest off-the-shelf CPUs into its phones, it made a hybrid. 2014's haul returned to Qualcomm.

Operating system

Each operating system has its pros and cons, depending on what you want.

iOS
Apple's iOS has a well-integrated ecosystem, a very full apps marketplace and a fairly intuitive interface, but you're pretty much locked into iTunes for content. If you already have a Mac, an iPad and/or an iPod, it's probably easiest to go with an iPhone.

iPhones have the advantage of receiving the same OS upgrade at the same time, and the newest OS is usually available on multiple devices. We're currently up to iOS 8.

Android
For its part, Android is the most customizable OS and a wonderland for tinkerers . However, most manufacturers and carriers add a specialized twist, which can lead to slower OS updates, and to an interface that may require a little more ramping-up to do straight out of the box. On the other hand, phone makers can use that custom layer to add a lot of software features that others just don't have.

True Android devotees should spring for the latest Google Nexus handset, or a Google Play Edition of a flagship phone. Android 5.0 Lollipop is the latest OS version.

Windows Phone
Then there's Windows Phone. Microsoft's OS has a simple, appealing interface, and Windows Phone 8.1 helps level the playing field with the Cortana voice assistant and a notifications center. Power users still may not find it quite as deep or as flexible as Android, and its app ecosystem isn't as robust. Still, solid hardware choices give Windows Phone a lift (especially on the budget end), and it has strong integration with Office and with Microsoft's other services.

BlackBerry
BlackBerry, once the premier brand of mobile communication devices, has been in dire straits lately. While many BlackBerry owners in the US have jumped ship and gone with iOS or Android smartphones instead, the struggling company is still releasing phones like the BlackBerry Passport.


Cutting-edge phone features

NFC
Short for "near-field communication," NFC is on almost all smartphones these days, now that Apple finally added it to the iPhone 6 and 6 Plus. NFC enables fast data exchanges between devices over short distances, just by tapping handsets together. It's essential in payment systems like Google Wallet and Apple Pay, and it can be used to transfer information from device to another, like photos. It's also used to quickly pair phones to Bluetooth devices, like speakers.

Wireless charging
Wireless charging isn't a new capability. Toothbrushes and other household appliances have been performing this trick for years. It's been slow to catch on for phones, however, despite the greater need for constant power on the go. Various standards are in the works to increase its charging power, and some markets benefit from consumer campaigns like wireless charging embedded in tables at coffee shops. Wireless charging is integrated into the phone or an external case, or can be achieved through a plug-in dongle.

Apple Pay lets you authorize transactions with your fingerprint. CNET

Fingerprint scanning
Apple popularized fingerprint scanning for unlocking the phone, but it's made its way into other smartphones since, most notably the Samsung Galaxy S5 and Note 4 in addition to the latest crop of iPhones. With some manufacturers, the feature doesn't always work on the first scan.

Apple was the first to integrate fingerprint scanning with payment authentication, which is part of the feature known as Touch ID. On the iPhone 6 and above, Apple Pay will also use fingerprint scans for real-world payments.

Heart-rate monitor
Go ahead and call health the next frontier, because that's it's a new area that device makers like Apple and Samsung are focusing on. Samsung's Galaxy S5 was the first smartphone to carry an LED heart-rate monitor, and it's present in other phones like the Note 4, the Note Edge and the Galaxy Alpha. Expect to see more of these crop up in wearables like smartwatches and fitness bands, and fewer on phones.

Curved screens
Why curve a smartphone screen? Because you can. The Samsung Galaxy Round and LG G Flex were the first, followed by the Samsung Galaxy Note Edge. A more ergonomic feel is one touted benefit, and so is having an immersive viewing angle. Displays like that on the Flex have an added claim: more flexibility can theoretically lead to reduced breakage. Mostly, though, curved screens seem to neither dramatically help or hinder.