Spectral analysis of surface waves (SASW) technique is an in-situ nondestructive method used for near surface soil site profiling. In the present study experimental uncertainties related to this method are assessed in connection with test configuration specification and data quality. Field experimentations have been conducted for this purpose with various spatial configurations of source to near receiver distance and inter-receiver distance under various impact source magnitudes and heights of fall. Based on the experimental findings, a method has been proposed to identify the frequency range of interest based on a threshold minimum cross power spectrum value. Further, it is proposed to consider subset stacking combination with good data quality which can be estimated based on weighted evaluation of the coherence of each frequency and importance of different frequency ranges. A procedure of obtaining the site specific dispersion curve is illustrated with due consideration to the issues associated with data quality and power spectra.