Science and engineering are the fields which deal with the complex computational problems. So, dealing with these problems requires a very robust platform and Grid Computing provides the required functionality. Geographically distributed heterogeneous resources define the Grid computing scenario. The major problem which arises in the area of Grid Computing is the task scheduling which tends to select the best resource for a given job. There are many scheduling heuristics (online and batch mode) are available but they are not able to achieve the maximum objectives. So, Quality of Service (QoS) based approach is required to achieve the maximum objectives. The QoS based approach keeps into account the QoS based characteristics for both the tasks and the resources. In this paper we study the different heuristics techniques for resource selection in Grid Computing and also we go through the need and significance of this QoS based approach in Grid Computing.