What guidelines were used by miller and urey when they constructed their experiment?

Guidelines used by Miller and Urey:

In 1952, Stanley Miller with the support of Harold Urey conducted the classic experiment investigating the original evolution of life from chemical substances. (abiologically)

Miller and Urey conducted experiments by setting up an apparatus trying to provide the proof that organic compounds can exist from inorganic compounds. His apparatus had conditions nearly similar to the time of life started and by the flow of electricity which had water , methane , ammonia , and hydrogen obtaining various organic molecules.