Handover is the mechanism that transfers information from one terminal to another as a user moves through the coverage area of a cellular system. Here the network selection is the handover decision process between various network environments. This handover decision will be either mobile or network initiated. In 2G GSM handover decision method especially concentrates on Received Frequency Signals (RFS). Upcoming technologies (3G/4G) the number of available networks increase the selection process should evaluate additional factors such as cost, network services, network terminology, system conditions, user and operators performances and needed energy to work in an exceedingly network.