The present guidance has been prepared by CEATI professionals and was specifically aimed at assisting the personnel involved with the implementation of the methods of ensuring energy efficiency and all relevant practices. The main emphasis has been made by the author on the refrigeration systems having a small and medium size. This publication would also help them to make proper technical decisions relating to the operation and day-to-day maintenance of the existing refrigeration systems; it would even be quite useful when applied to the modification or re-configuration of the subject systems. The readers will get necessary guidance that is very difficult to obtain in other publications. Various refrigeration systems are characterized in this guide; quick reference on various established techniques of performance optimization is provided; the main procedures of the performance testing have been reviewed. In short, this is a definitely excellent source of information recommended to be used by any persons who are directly involved in any activities that are relating to the refrigeration systems due to the amount of the information contained. Please note as necessary that the specialists operating and maintaining the refrigeration systems are expected to follow all applicable safety procedures and techniques prior to the commencement of any operations.