Glenn Fleishman of WiFiNetnews has an in-depth article in PC World that explains and solves common Wi-Fi problems.
It documents the current state of WiFi setup and maintenance, reviewing common troubles and explaining solutions, clearly. It's an excellent overview – no matter what your level of expertise – and provides a good snapshot on the state of the art.
Bookmark the PC World story, you'll be glad you did. Of course, for in-depth Wi-Fi testing and reporting, you just can't beat Tom's Networking. [Daily Wireless]