Wireless networking often works simply, but problems can be tricky to trace. This article aims to help with the most important pointers.
Start with About.com's 10 Tips for Wireless Home Network Security.
Use WPA2 Personal (also known as WPA2 Pre-Shared Key, PSK) rather than WEP as the encryption protocol.
Wireless networks can be hampered by interference from a neighbor's network using the same frequency band, or other equipment such as a microwave or cordless phone.
MacWorld published this helpful advice on wireless network interference in May 2010:
If you want to scan for interfering wireless networks, try KisMAC. There are 11 channels (14 in Japan) in the 802.11 2.4GHz range, and you want at least five channels of spacing between access points that are within range of each other, to avoid interference. So, for example, if you scan with KisMac and notice that you have a neighbor using channel 1 and another using channel 6, then you want to use channel 11. The Apple products are usually fairly good at picking a good channel when they're set to "Auto" channel mode, but not always.
Intermittent problems, especially if they affect just one out of multiple computers, could be down to a software issue specific to that machine. It might be worth noting the times the dropout occurs and seeing if anything is showing up in the Console logs at around the same time. Try typing "Airport" into the Console search-field and see what comes up.
If it is not software, it could also be a loose or poorly fitted Airport card in the laptop.
Try connecting a computer directly to the modem; if this works, the problem is probably with the router. When doing this, powercycle the modem by pulling its power out for a few seconds, then reconnect. Whatever connects to it first gets "married" to the modem, and the modem always assumes that device is connected to it. Powercycling the modem starts it at zero, and tells it to check the network port to establish a connection.
Mac.tuts+ posted this helpful article in November 2012:
This page is a summary of emails posted on the Mac Ministry List in December 2010–November 2012 by Aaron Hunyady, Andreas Jodner, Jon Gardner, Peter Connolly, Allan Crowson, Chris Howard, Darrell Fulwilder and Hank Lee.