This is a revised edition of a master´s thesis, which purpose was to find general principles of how to create realism. Here, the focus is on ideas and results that could be used in wargaming. Most of the matter comes from literature studies, but also from studies of some wargames, microanalysis of recorded materials and interviews of participants in wargames. There is no need for every detail to be realistic, but the participants should feel that it is realistic and that they have an influence on the course of events. Participants in wargames should have their focus on the reality of the game, which will be easier if the scenario is interesting and sufficiently complex. "Lack of contradictions" is probably the most important factor. Irrelevant incidents and information that interfere with the game must be avoided. Uncertainty about the course of events and new unexpected information can lead to better attention and engagement. This points to the use of closed games. The same effect could be achieved by using two-sided games, where men´s disposition for competition can be useful. All participants must respect the rules of the game. They must not manipulate or create new conditions. This is true even for those who conduct the wargame or staff exercise. They can easily spoil a game by too drastically change the conditions of the scenario.