The economically valid modelling of practice firms is a very important aspect when working with practice firms as well as a prerequisite for students to understand economic processes, relations and real-life market structures. However, empirical studies show that there are still discrepancies between the requirements and the actual situation in Austrian practice firms. Therefore, the particular research interest of the current master?s thesis concerns the identification of requirements resulting from an economically valid modelling of practice firms as well as the determination of corresponding instruments to fulfil the identified demands. The results of the present paper can be summarized in the following statements: When choosing the object of the practice firm, the current market situation must be taken into account. More-over, the partially antiquated organisational structures need to be enhanced in terms of a process orientation. Management also needs to consider the principle of the completion of action in practice firms. Furthermore, successful working processes in practice firms rely on knowledge and information based internal communication structures. In addition, the design and continuing actualization of a mission statement and guiding principles is necessary in order to create mutual values in practice firms. In terms of corporate planning, the regulatory cycle of action must be closed in practice firms to guarantee the quality of the working processes. The present paper also discusses a range of adequate instruments to fulfil the requirements mentioned above. Especially the business plan turned out to be a comprehensive planning and construction tool and is therefore highly suitable to be used as an instrument in practice firms.