Usually at stochastization of mathematical models stochastic term is introduced as the external noise. This action can only characterize the environment, but not itself system under study. There is a need introduce the stochastic term in concert with deterministic, that is, to receive both parts of one and the same first principles. A method is presented stochastization of models describing the single-step processes (birth-death processes). The method allows to obtain deterministic and stochastic components from first principles that allows us to consider these pieces matched with each other. For equations used notation of chemical kinetics. In addition to simple the law of mass action can be used trophic functions. Application of the method demonstrated by the environmental and telecommunication models.