Many companies have started deploying the IEEE 802.11b WLAN in places such as airports, hotels, etc. This is mainly due to the availability of affordable Wi-Fi services and related consumer products, such as laptops PDAs, gaming devices, digital cameras, etc. The 802.11b technology is particularly attractive due to its maturity and low cost. The 802.11 capability has been included as standard equipment in many laptop computers and hand-held devices. IEEE 802.11 WLANs are common in home and urban areas. These networks are often managed by non specialists, that leading to unplanned topologies and interference and therefore reduces its performance. Several algorithms and technique was developed to avoid interference. This paper describes different methods used for channel allocation and AP placement.