Publisher Summary The chapter explores the physical medium of wireless local area networks (WLANs), and the ways in which it can and must be manipulated to have an effective WLAN. This coverage ranges from theory to practice while conducting site surveys in advance of WLAN setup. The most important part of WLAN implementation is deployment planning. A poorly planned deployment is much worse than no deployment at all. If appropriate planning is not done, wireless LAN deployment can be a complete failure because of its inability to function or its inability to properly serve user needs. Site surveys are critical to both the initial planning stages of Radio Frequency deployment and the ongoing maintenance of the WLAN. These are explored in detail in the chapter and a sample site survey form is provided to get one started. Interference detection and how this step of planning can help one to successfully deploy WLAN are also discussed in the chapter.