As an introduction, the simple formalism for determining/describing the structure of liquids and amorphous materials is recalled, followed by a reminder of the standard evaluation procedure of diffraction data for disordered systems. Problematic issues, with an emphasis on the Fourier transformation between reciprocal and real space information, as well as the information content of measurable diffraction data, are discussed in some detail. At this point, arguments as to why a novel structural modeling method was needed are provided. Then the concept of Reverse Monte Carlo modeling is introduced, followed by a detailed description of the RMC algorithm. Finally, examples of applying RMC on simple liquids, from liquid argon to metallic melts, are presented.