STEP 1: GET THE GEAR
Start with your computers. Every PC, laptop and Apple computer in your house will need a wireless antenna, which comes in the form of a slim card, or adapter, that either slides into a slot or plugs into a USB port. There are a number of these cards for PCs. For a Mac, you'll need what's called an Airport card, which comes built in on newer models.
The heart of your network will be a wireless router--a box with an antenna that shuttles signals between each of your computers and the network. Choose one that has extra Ethernet ports and a built-in firewall. You can get one for $100. Linksys, Belkin, Buffalo, D-Link, even Dell and Microsoft sell them. Before you buy one, read reviews at cnet.com or wifiplanet.com
There are a few different wi-fi standards, but home users need to know about only two of them: 802.11b and 802.11g. Don't sweat it. They are compatible with each other. But these days, it makes sense to go with all G. It moves data around about four times as fast as B. You won't download Web pages any more quickly, but you will be able to move audio and video files between computers (or from a PC to, say, a wi-fi--equipped stereo or TV) at a faster clip. Busy households with multiple users will also see a difference.
Just be sure everything you buy is stamped WI-FI CERTIFIED so you know that all your gear will work together. (Important: if you bought any G products before Sept. 1, check the manufacturer's website for a free upgrade.) A laptop using a B card will talk to a G router (and vice versa), but it will connect at a slower speed. And experts warn that mixing B and G drags everything down.
Mac and Windows computers, even those running older operating systems, should be able to coexist peacefully on your wireless home network. But the more you mix it up, the more complicated things can get. In a perfect world, all your Windows machines would be running Windows XP (which was designed with wifi in mind), and all your equipment would come from the same manufacturer, so when you call tech-support folks, they can't pass the buck.
STEP 2: SET UP THE STUFF
Follow the product manuals closely. Whatever you do, don't click on anything or change any settings you're not sure about. It's much harder to fix a mistake than it is to go back and complete a step that you skipped the first time through.
Before you begin, contact your Internet service provider to get your account's IP address and other numbered settings, such as subnet mask, default gateway and DNS addresses. Keep them handy. At some point you may be prompted to key them in.
To set up, first turn everything off. Disconnect your cable or DSL modem from your computer and plug it into the back of the wireless router. Use another Ethernet cable to connect the router to the computer's Ethernet port (the same one you had the modem plugged into). You will set up the router by running the accompanying CDROM on this computer. (Tip: It's a good idea to keep at least one computer tethered to the router, says Synergy Research analyst Aaron Vance. That way, if your wireless connections fail, as they occasionally will, you'll always have at least one computer ready to go online, and you'll always be able to check or tweak the router.)