Here a methodology is presented to outline the steps of developing a process simulation as a tool for decision making at the enterprise level with emphasis on pre-design model (analysis input) stages, through study of the literature and experience of the senior author essentially established by evaluating the steps (Banks, 2005) and considering their application to micro and small enterprises mainly based on the findings of three garment companies of its kind in the city of Bogota yield results in a novel way that simplifies and makes more practical the use of simulation.