Proper decision-making is one of the most important capabilities of an organization. Therefore, it is important to make explicit all decisions that are relevant to manage for an organization. In 2015 the Object Management Group published the Decision Model and Notation (DMN) standard that focuses on modelling business decisions and underlying business logic. DMN is being adopted at an increas-ing rate, however, theory does not adequately cover activities or methods to guide practitioners mod-elling with DMN. To tackle this problem this paper presents a method to guide the modelling process of business decisions with DMN. The method has been validated and improved with an experiment using thirty participants. Based on this method, future research could focus on further validation and improvement by using more participants from different industries.