Recently occurred critical system states have triggered a broad discussion between Distribution System Operators (DSO) and Transmission System Operators (TSO) about the actuality and validity of grid restoration plans all across ENTSO-E. Generally being in the responsibility of the TSOs, the role of DSOs in the restoration concept in case of islanded grid restoration is not yet clearly defined and has been a topic in many discussions. Beside the organizational aspects regarding grid restoration, various technical requirements have to be considered. This paper highlights the key aspects of well-known as well as newly arisen topics. Furthermore, to guarantee a successful grid restoration, a 3-step approach is introduced. It contains islanded grid operation tests, the development of an accurate and reliable simulation model and the simulator-based training of the operators.