As always, this is a general guide aimed at mainstream, nontechnical consumers who dwell on common tasks such as email, instant messaging and surfing the Web; managing and lightly editing photos, videos and music; and using basic office applications. It is not intended for heavy gamers, video producers or corporate buyers.

There’s a vast variety of laptop models, but this guide is meant to cover the most common types of laptops, those with screens from about 12 inches to 17 inches, and weights ranging from around 2.5 pounds to 7 pounds.

For this column, I’m not including the category of tiny machines now called netbooks, with screens under 10 inches. I am also ignoring the huge, heavy laptops with screens larger than 17 inches that are primarily aimed at gamers.

Even the remaining mainstream machines range wildly in price, from bargain-basement models at $350 to high-end ones that can top $3,000. In my experience, the top brands for technology and reliability are Apple and Lenovo’s ThinkPad line, but various models from Sony, Hewlett-Packard, Toshiba and Dell are also worth investigating.

So, here is a quick guide to the key factors you should consider when buying a laptop.

Size: If you are a constant traveler, think about the subnotebook models, which generally weigh 3 pounds or less. There are two types of these. The classic subnotebook has a small screen, 12 inches or less, and a cramped keyboard. This year, a new type emerged, with a full keyboard and a normal 13.3-inch screen packed into a thin, light body. There are two of these: the MacBook Air from Apple and the Lenovo ThinkPad X300. All subnotebooks are relatively costly, typically ranging from $1,500 to over $3,000.

If your laptop will mostly stay at home, the office, or in class, a 5-7 pound machine with a screen of either 13.3 inches or 15.4 inches is the best bet. A well-equipped model in this class is likely to run you between $800 and $1,200. Typical models in this class are the Dell Inspiron 1525, the HP dv6700 and the Apple MacBook.

Windows vs. Mac: This is the eternal question. In my view, Apple’s Leopard operating system is faster, better and far less prone to malicious software than Microsoft’s Vista operating system. And the Mac laptops also come with better built-in software. The $1,099 MacBook is a solid, fairly priced machine, and the $1,999 MacBook Pro is even better. Both also can run Windows.

But Windows laptops are often less expensive, tend to have a greater variety of ports and slots, and come in more styles and sizes.

Apple’s MacBook

Operating system: If you are buying a Windows laptop, be aware that Vista is slower than Windows XP, in my experience, and still has compatibility issues with add-on hardware and software. If you’d prefer to stick with XP, you will find that many fewer models are available with it. And Microsoft has decreed that after June 30, mainstream, name-brand laptops will no longer come pre-equipped with XP.

Video: I recommend getting an LED-powered screen, which is brighter and saves power. Also, if you are choosing Vista, or if you do a lot of converting video for use on portable devices, consider getting a laptop with a separate video card inside that has its own memory.

Memory: If you’re buying an Apple laptop, two gigabytes of memory is plenty. If you’re using Vista Home Premium, I’d consider three gigabytes for best performance.

Processor: Any dual-core processor will be fine. Don’t pay a penny extra for faster processor speed.

Storage: In a mainstream laptop that will be your main computer, look for a 160-gigabyte hard disk or larger. A new kind of storage, called SSD, or solid state disk, is now available. But it is still way too costly for most users, and at the moment is available only in smaller capacities.

Battery life: Many laptops today rarely spend time away from an electrical outlet. But if yours will, look for a battery life of at least three hours between charges.

Wireless: Make sure your new laptop has the new, faster “N” version of Wi-Fi built in. Many cheaper laptops don’t. You can also get a cellphone modem built in, but they are costly and carry a monthly fee. You can always add an external cellphone modem later.

Other features: A built-in camera and microphone can be quite useful, and so can a feature on some Windows machines that allows you to play music and videos without fully booting up the computer.

Don’t let yourself be swayed by sales pitches, or by fanaticism for or against Windows or the Mac. Think hard about how you use your computer and what your budget will allow, and stick to those priorities.

• Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.

I’ve been testing two of the latest efforts to crack that problem. The first is from Toshiba, a company that once dominated the laptop world, but has since slipped badly. The other is from Dell, best known for larger, clunkier laptops. Both machines are stylish and worked fine in the tests, but each has flaws that might give a buyer pause.

These two new laptops, which use Intel’s Core 2 Duo processor, are very different in size. The Toshiba Portege R500 weighs just 2.4 pounds, has the footprint of a standard sheet of paper and is only about ¾-inch thick at its thinnest point. Yet it squeezes in a DVD drive. It sports a 12.1-inch widescreen display with very good resolution. The screen is lit by LEDs instead of by traditional lamps. That makes for more brightness and saves power.

The Dell XPS M1330, while still relatively small, is larger than the Toshiba. It weighs a hair under four pounds, has a larger footprint and is thicker. It falls into a hot new laptop category that features 13.3-inch widescreen displays — a size considered a good compromise between the small displays on the lightest laptops and the larger ones on the heavier models. The M1330 has some very un-Dell-like aspects to it, such as a choice of three lid colors and a slot-loading DVD drive that doesn’t require a pop-out tray.

Toshiba claims the R500 is the world’s thinnest notebook with a built-in DVD or CD drive. Dell claims the optional LED version of the M1330 is the thinnest with a 13.3-inch screen.

The Toshiba starts at $1,999 for a unit with a 120 gigabyte hard disk, a gigabyte of memory, and built-in Wi-Fi and Bluetooth wireless networking. The Dell starts at $1,299 for a model with a 120 gigabyte hard disk, a gigabyte of memory, built-in Wi-Fi (but not Bluetooth) and standard display. An LED display costs $150 more; Bluetooth is an extra $20.

I tested the base model of the Toshiba R500 and found that it performed well. My particular machine came with Windows XP, though Windows Vista is also available in a model that costs $150 more. The tiny silver computer handled everything I threw at it, including Microsoft Office, the Firefox Web browser, the iTunes music program and more.

Toshiba’s Portege R500, top, and Dell’s XPS M1330

In my tough battery test, where I turn off power-saving features, maximize screen brightness, turn on Wi-Fi and play an endless loop of music, the R500 lasted an impressive three hours, 44 minutes. I estimate that in more normal use, you could get five hours of battery life.

But my test Toshiba, a production unit, had a major flaw: The DVD drive didn’t work. Apparently, the lens on the drive had come loose in shipping. Toshiba sent another unit with a working drive, but this is a major issue because the machine uses a new, very thin type of DVD drive that seemed fragile to me.

In fact, the R500 lacked a solid feeling overall. The keyboard was OK, but the touch-pad buttons seemed flimsy and stiff, and I had the impression that this was a computer you’d have to treat gently. It also had trouble reconnecting with my Wi-Fi network after waking up from its sleep state. And it was loaded with the trial software and offers I call craplets.

The Dell XPS M1330, on the other hand, felt solid through and through. From its crimson cover to its wedge shape, it’s also a handsome laptop. The unit I tested had the LED screen and a full complement of options, which would have brought its price to $2,188.

Like the Toshiba, the Dell speedily handled Microsoft Office, Firefox, iTunes and other software. Its Wi-Fi worked very well. My test model used Vista, and had the extra memory and souped-up graphics Vista needs to work well. The M1330 isn’t available with Windows XP. To Dell’s credit, it can be ordered with no craplets on it, for no extra money. But because it uses Vista, it starts up painfully slowly. A reboot took more than four minutes.

The big flaw on the Dell is battery life, a major downside for a machine meant to travel. In my test, the M1330 lasted just two hours, 27 minutes; so, you’d be lucky to get 3.5 hours out of it in normal use. Dell says the base model would do better because it has a wimpier, but less power-draining graphics system. You can get a bigger battery for $30 more, but it makes the machine larger and heavier.

The Dell XPS M1330 is a good, solid, mobile computer that needs better battery life and can get expensive once you start ordering options. The Toshiba R500 seems like a dream machine for travelers, but its DVD defect is worrisome and you may have to treat it like glassware.

• Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital Web site, http://walt.allthingsd.com.

Most of the major specs I recommended two weeks ago in my annual spring guide to buying a computer hold true for laptops as well as desktops. That guide can be found at walt.allthingsd.com/guide. But buying a portable involves additional factors, so here are some tips for making laptop purchases.

First, you may want to wait to get that new laptop until later this year or early in 2008. There are a number of interesting new hardware features coming. One is called a “solid-state drive,” or SSD, which replaces the traditional hard disk with a faster drive made of memory chips like those used in digital cameras. Another is a “hybrid hard drive,” or HHD, which combines memory chips with a standard hard disk, for faster start-ups.

Also, more and more laptops will be using light-emitting diodes, or LEDs, to light up their screens — a method that promises to be both brighter and less power-hungry.

You also may want to wait for laptops with a new type of Wi-Fi wireless networking built-in. It’s called “N,” and promises to be faster and to have longer range.

For Windows Vista users, another new laptop feature coming soon is a small screen on the lid called a SideShow, which can display calendar appointments and new emails.

Even if you don’t wait, there are some features to know about that aren’t available on most desktops. One is a built-in Web camera and microphone, highly useful for making video calls and recording videos to be posted online. Another is a feature that allows you to play music, videos or DVDs without booting up Windows.

In addition, if you travel a lot, you may want something called a built-in WWAN, or Wireless Wide Area Network. This is essentially a cellphone modem that makes Internet connections over a cellular carrier.

Another key feature is a new kind of slot on the side of most laptops for add-on cards, like wireless modems. It’s called an ExpressCard slot and, confusingly, it comes in two sizes. Your old-style cards, called PC Cards, won’t fit in these new slots, so unless you want to buy new cards, you might look for a laptop that has both the old and new slots.

Battery life, weight and size remain crucial on laptops, unless you are buying a huge “desktop replacement” laptop, which will rarely leave the house or be unplugged. For everyone else, I recommend finding a laptop that offers at least three hours of battery life on a single charge, without requiring you to dim the screen so much you can’t see anything.

Most laptops cluster around the six-to-seven-pound range, which is fine for occasional travel, or for carrying between classes, or between home and office. But if you are a frequent air traveler and have the budget, shoot for a laptop that weighs four pounds or less and is small enough to use on a seat tray in coach even when the person in front of you reclines.

The most expensive laptops are at the extremes–huge, multimedia machines and ultra-portable models for hard-core road warriors. Most well-configured Windows laptops, with typical 15.4-inch screens, are between $900 and $1,500.

I find that laptops with 13.3-inch widescreen displays make a nice compromise between mobility and power. At the moment, there are very few brand-name models in that size, notably Apple’s $1,099 MacBook, which weighs 5.2 pounds; and Sony’s Vaio SZ line, which weighs 4.1 pounds but costs roughly twice as much. More 13.3-inch models are coming later this year from other manufacturers.

Finally, there’s the perennial issue of Windows versus Mac. Apple’s two laptop lines, the MacBook and MacBook Pro, are very good. They have better built-in software than any Windows laptop I’ve seen and don’t suffer from the security issues that plague Windows. And they can even run Windows software, if you need that.

But the Mac laptops lack some features that are common on Windows portables, such as slots for camera memory cards and built-in cellular modems. And the MacBook even lacks an ExpressCard or PC Card slot.

Among Windows machines, I think Sony and Lenovo make especially well-designed laptops, but almost any name brand would be fine.

Addendum: I’m happy to say there is a new, expanded and redesigned online home for all my columns. It’s at walt.allthingsd.com and access is free. It contains the current versions of the columns with the accompanying videos, plus a searchable two-year column archive and a new blog called Mossblog, which I will update occasionally.

This new column home page is part of a larger new Web site called All Things Digital, at allthingsd.com. In addition to my columns and blog, it contains technology news, analysis and opinion from journalists Kara Swisher, Katherine Boehret and John Paczkowski, and guest blogs from prominent technology figures.

My columns will still be published on The Journal’s main Web site, WSJ.com, which is available to paid subscribers and includes a much larger archive, going back more than a decade.

• Email me at mossberg@wsj.com