This paper provides a summary of the essence and the results of the author's reduced potential curve (RPC) method hitherto scattered in a large number of scientific papers, which he hopes may serve for the use and further development of this method by other interested scientists. The RPC method makes possible a systematic study of the internuclear potentials of the ground and excited states of diatomic systems in a unique RPC scheme. Interesting and so far unknown regularities and rules (laws suggested by the quantum mechanical background) appear in the RPC scheme. With the use of these ‘RPC rules’, the RPC formula and its parametrized generalization, the Grpc formula, may be used for various practical applications of the RPC method such as: (a) detection of (even small) errors in the potentials constructed from the spectral data or errors in the analysis of the spectrum of a diatomic system, (b) detection of errors in the values of the molecular constants, (c) detection of errors in the adiabatic potentials due to perturbations, (d) detection of anomalies, (e) estimation of the dissociation energy, (f) correction of errors in the potentials mentioned above, and (g) construction of the internuclear potential of a diatomic system and calculation of its spectrum from the spectral data of another diatomic system or from anab initiocalculated theoretical potential. The rules and the structure of the RPC scheme and the applications of the RPC method are demonstrated in numerous examples and further prospects are discussed.