A functioning maintenance management is essential for a successful company. Although the industry knows about that fact, in a lot of companies the significance of maintenance is relatively low. A large part of the companies is still practicing only reactive maintenance activities, this leads to high costs. To reduce those costs, it is necessary to deal with the different maintenance strategies and their selection. This thesis should provide an overview of the subject maintenance. For this purpose, the basics of maintenance are explained in the first chapter. This includes the maintenance strategies, the failure behaviour and certain key figures. After that the correct procedure for selecting the right maintenance strategy and the optimization of maintenance cycles is explained. Industry 4.0 also concerns the maintenance management. Due to that this thesis shows the revolution from the reactive maintenance towards maintenance 4.0. It is explained, which possibilities come up with the implementation of a maintenance 4.0-system and how it is structured. To conclude the thesis practical examples are given. For that three different types of machines were chosen, a baler, a bag opener and a single-shaft shredder. The three examples operate at two different treatment plants (Vienna, Graz) of the Saubermacher Dienstleistungs AG. As the locations differ according to the available databases, the choice of the optimal maintenance strategies is carried out in different ways.