Nowadays, IEEE 802.11 WLANs have been widely deployed in parallel with the growth of mobile devices. However, due to design choices and requirements, the communication range of the IEEE 802.11 standard is limited. Therefore, WLAN coverage over a large geographic area is provided using multiple access points (APs). Due to the mobility of mobile stations, a station might move and lose the signal of its associated AP. In that case, the station tries to maintain its wireless connectivity by associating with a new AP in a process known as handover. However, providing handover with guaranteed QoS is a challenging task for real-time applications, such as VoIP, video/audio streaming, and video conferencing. In this paper, we propose an efficient handover mechanism that can provide fast handover with guaranteed QoS for real-time applications in WLANs. With the help of the IEEE 802.21 information server (IS), a smart selective channel scanning method is deployed on mobile stations. Selective channel scanning enables stations to filter out the unavailable channels, and organize reliable group of channels to scan during the upcoming handover process. Simulation results show that the proposed scheme reduces the channel scanning delay in handover process, increases the overall throughput and provide QoS for real-time applications compared to the conventional handover scheme.