Josh Miller/CNET

If you own a desktop computer, you'll need a monitor. The best overall monitor right now is the Dell UltraSharp U2713HM . It delivers fantastic performance on an extreme-definition (2,560x1,440-pixel), 27-inch screen, with great ergonomic options, and a useful assortment of connections, for $800. If that number sounds too rich for your blood, the Asus PA248Q sells for as low as $310, with a 24-inch, 1,920x1,200-pixel screen, ergonomic options, each major video connection, and unique and useful customization settings. Finally, if money is no object and owning the absolute best performer is a priority, the HP DreamColor LP2480zx should be your one and only choice. At $2,900, however, it's obviously not for everyone. Check out the rest of CNET's list of top monitors for more options.

Three rules for buying a monitor

1. Know your needs

There are plenty of important questions you should ask yourself before you plop down cash for a monitor, but the most important is, what are you planning to use it for?

James Martin/CNET

Are you looking for a basic window on to e-mail and the Web? How important are ergonomic options to you? What about the onscreen display (OSD) settings? How detailed should they be? What about size? How much screen real estate do you require? Are you planning to run concurrent programs? What about connections? What type does your computer support?

2. Warranties and support matter

Make sure your chosen manufacturer offers a money-back guarantee. Most displays will show any problems right out of the box or within the first month or two of use, so you want to be able to return it for a refund or an exchange with a minimum of hassle. A 90-day return policy is standard, but this varies among retailers (many online retailers give you only 30 days). Also, beware of restocking fees.

Next, consider the warranty coverage. Most companies offer two to three years of parts-and-labor coverage; anything less is suspect. Make sure that the backlight is covered by the warranty. Also note a company's policy on defective pixels; one or two defects are to be expected, but if there are many, you should be able to return the unit for exchange or a refund.

James Martin/CNET

You're far less likely to need technical support for a monitor than for a computer system or a software program. Still, it's good to know that there's someone you can call if trouble arises; look for toll-free support numbers and weekend coverage.

Be sure to keep all of the packing material for your monitor. If you should ever need to return it or ship it back for warranty service, you'll need the packaging. Monitors can be bulky, fragile, and extremely difficult to protect adequately. You don't want to end up improvising when shipping it.

3. Performance is key

When you're using your monitor, you're staring at its screen. Obvious, yes, but it's important to make sure you like the types of images it displays before you buy. The best way to do this is obviously to see it in person. Monitor reviews are helpful when deciding between multiple monitors, but nothing can determine a monitor's image quality better than your own eyes. If possible, try before you buy.

James Martin/CNET

Screen size

17- to 20-inch

Many 17-inch monitors have 4:3 aspect ratios, which may not fit the needs of many people today who have grown accustomed to wide-screen displays. Nineteen-inch screens are typically wide screens with a 16:10 aspect ratio. Unfortunately, their resolutions don't usually break the 1,366x768-pixel barrier. As for 20-inchers, you likely won't find one these days not sporting a 16:9 aspect ratio with a 1,600x900-pixel resolution. Not the sharpest resolution, but at least HD (720P) movies will play at their natural aspect ratio. Prices for these sizes can range anywhere from $100 to $350.

21.5- to 23-inch

The 21.5- and 22-inch monitors are the smallest with 1,920x1,080 resolution and at this size, monitors begin to feature more useful connections like HDMI and even DisplayPort. Prices in these sizes range from $130 to up to $500 depending on the panel technology, which we'll discuss later.

Josh Miller/CNET

24-inch

Twenty-four-inch monitors are in a class all their own. They're the only monitors that function at both 1,920x1,080- and 1,920x1,200-pixel resolutions. Good ones (and by "good" ones, I mean those with at least an IPS panel) can range from $300 to over $700 and, in some cases, over $2,500.

27- to 30-inch

Twenty-seven-inch monitors are capable of 1,920x1,080- and 2,560x1,440-pixel resolutions. Prices start at $250 for the lower-resolution models, but can reach well over $1,000 for extreme-definition versions. The 30-inch displays run at 2,560x1,600 pixels, start at about $1,100, and can reach upward of $3,000. However, with the advent of extreme-definition 27-inch displays, 30-inch displays are having a difficult time justifying their price.

James Martin/CNET

Key considerations

Panel type

The CRT has effectively been replaced by its thinner and brighter sister, the LCD. Under the umbrella of LCD technology, there are a few choices to make before buying a monitor. First, you'll have to decide which panel technology is right for you.

Twisted nematic (TN)
The main advantages of TN panels are their fast -- usually 2ms (or less) -- response time and their low price. Their major disadvantages are narrow viewing angles, relatively low brightness, and inaccurate color reproduction.

Josh Miller/CNET

Vertical alignment (VA)
VAs have better viewing angles than TNs, better color reproduction, and typically a much higher maximum brightness. Also, they tend to have the lowest black levels of the four major panel technologies. Unfortunately, a VA panel's response time and input lag are not quite as fast as a TN panel's, and monitors using them can cost anywhere from $400 to $800, and sometimes more depending on the panel's size. Also, you can expect a VA-based monitor's profile to be wider than a TN's.

In-plane switching (IPS)
IPS-based monitors are usually the most expensive; however, monitors using e-IPS panels can cost as little as $150 (for a 22-inch monitor). They also tie with PLS for the best viewing angles of all the technologies and produce the most accurate colors; however, their blacks are not as deep as VA panels'. IPS monitors are the slowest of the bunch in both response time and input lag.

Josh Miller/CNET

Plane-line switching (PLS)
PLS is a new panel technology from Samsung that debuted with the Samsung Galaxy Tab 10.1 tablet, but the first monitor to make use of the tech was the Samsung SyncMaster S27A850D . PLS panels sport viewing angles as wide as IPS, while offering higher brightness at a lower cost in power consumption. According to Samsung, production costs for PLS panels are 15 percent lower than for IPS, as well.

Backlight

Let's clear this up right away: LED and LCD technologies are not mutually exclusive. To ask what the differences are is like asking what the difference is between Vibram FiveFingers shoes and rubber soles.

The term LCD stands for liquid crystal display. LCDs use liquid crystals to express what you see on the screen. The crystals act as a shutter for the backlight, and, depending on the type of charge given to them by the monitor's built-in electrodes, the crystals will either allow light through to the user or shut it out, thereby allowing the pixels to express their appropriate colors, making up what you see on the screen.

Josh Miller/CNET

LED-based monitors are still LCDs (they still use liquid crystals to express images onscreen), but they use a different type of backlight than what is normally used. Most monitors of the last few years have used cold cathode fluorescent (CCFL) tubes as their backlight of choice.

Types of LED backlights on monitors

WLED
This is the type of LED backlight most commonly used in today's monitors and features white LEDs aligned along the edge of the monitor matrix, right behind the liquid crystal array.

EL-WLED is the cheapest and smallest of the three technologies, which is why it's the most widely used. WLED backlights typically draw much less power than any other backlight tech.

RGB LED
Instead of using white LEDs on one edge of the screen like the previous technology, RGB LEDs are aligned all over the panel matrix. Each individual light is capable of producing red, green, or blue light. This gives the display access to a high color gamut with colors more accurate than what's possible on WLEDs. RGB tech is very expensive and doesn't permit a thin design.

Josh Miller/CNET

Connections

DisplayPort
Heralded as the successor to DVI and HDMI, DisplayPort is a higher-bandwidth connection that could facilitate thinner and lighter monitors as they would no longer require special circuitry (and hardware to run that circuitry) to receive a video signal. We've seen a fairly low adoption rate of the format thanks to comparatively low profit margins and the industry's reliance on legacy ports like VGA; however, things began ramping up in 2012.

In 2013, so far I've noticed a increase in ubiquity of the format, based on the admittedly few monitors I've gotten hands-on time with. However, judging by the specs of many new monitors from Dell, HP, Samsung, and Asus, DisplayPort appears to be gaining solid traction. It'll be interesting to watch how its adoption plays out through the end of the year.

DVI
Some newer monitors forgo digital visual interface (DVI) in favor of HDMI. If this is the case with the monitor you're interested in, make sure the monitor includes a DVI-to-HDMI cable or that your video card supports an HDMI connection. Having said that, we recommend getting a monitor with at least one DVI connection.

HDMI
An HDMI connection is used to connect the display to a high-definition source, such as a Blu-ray player, video game system, or DVR-based HD cable/satellite set-top box. HDMI connections are extremely common these days and it's the exception now when a monitor, 22 inches and larger, doesn't have one. If you're planning to use your monitor as a television, this is an essential feature.

Josh Miller/CNET

A few tips on how to look for what you want

Viewing angle: Look at the monitor from different angles and be aware of how much the colors shift or if the screen darkens. Also, pay attention to the angle when the screen begins to look different. Colors and brightness should not change when viewing the screen from an off angle, either from the sides, top, or below. TN panels will be the most egregious offenders.

Text: Go to a Web site and scrutinize the legibility of small text. Firefox lets you change the font size from its options menu. Also, be aware of any color-tint problems when viewing black text on a white background.

Accurate colors: View something you're familiar with, like a digital photo of a loved one or colleague you see every day, on the monitor; notice how different the colors in the picture look on the monitor.

Josh Miller/CNET

Glossy screens: These can seemingly increase the contrast of movies and games. Some people don't appreciate the extreme reflectiveness, however. View both glossy and matte screens, and decide which looks better to you.

Low black level: The closer a monitor can get to displaying black, the better. True black is elusive; the most you can hope for is that a monitor displays very dark gray. Check out dark scenes in movies, and notice how dark the black gets without actually losing the detail of a scene.

An adequate graphics card is a necessity

What's going on inside your computer can have a profound effect on what's displayed on your monitor. If you hook up a 4- or 5-year-old PC to a top-of-the-line new monitor, there's a good chance your graphics card will need an upgrade to give you the best possible image quality. You'll need a card that supports your interface, be it DVI or HDMI, and it will need to support your monitor's resolution -- this is especially important on 27-inch models with 2,560x1,440-pixel resolutions. Sometimes, improving your graphics card's performance can be as easy as installing a driver upgrade from the manufacturer's Web site.