In the framework of international trading, new regulations are being drawn up concerning safety and in order to prohibit counterfeit goods. Due to the short delays imposed by Customs, the trend is still toward paperless trading. As a consequence, a better process and software interoperability is needed between the different actors of trading (customer, supplier, Customs...); a first step in software interoperability consists in process modeling. This paper presents a pragmatic guideline to generating successfully the business process model. The original aspects are first to use BPMN (Business Process Modeling Notation) for the representation of all types of flows (and not only information flows), and second to propose BPMN business patterns for the international trading purpose.