Strategic sourcing plays a critical role in supply chain planning. Supplier selection represents one of the most important functions to be performed by the purchasing department that determines the long-term viability of a company. The supplier selection is a multi-criteria problem, which includes both qualitative and quantitative criteria. In order to select the best suppliers, it is necessary to make a tradeoff between tangible and intangible criteria, some of which may conflict. This paper provides an overall picture of research on Supplier Selection Process (SSP) and supplier selection practices. It deals with the 'supplier selection problem', where a state of the art is presented. We summarise the different selection criteria, the various problems of suppliers' selection and the existing methods to solve these problems. Furthermore, emerging issues and challenges resulting to scope for future works on supply chain procurement activities are identified and some clear guidelines for future research are proposed. It is aimed that the findings will lead to new research settings together with the directions for future research.