The Unified Modeling Language (UML) is now a standard means of expressing object-oriented analysis and design (OOAD) for the Object Management Group since 1997. The UML is called a modeling language, not a method. That is, the modeling language is the graphic notation that methods use to express design. However, the principles or guidelines for each UML notation modeling are lacking and those are crucial for the UML modeling. To address this important issue, this study utilizes research and development method to investigate the guidelines for each UML notation modeling. An example of war game is used to illustrate the guideline and application. With these guidelines, analysts can more easily use the UML notations to express OOAD and thereby improve the efficiency and effectiveness of UML modeling.