Currently there is a tendency to more and more use EEG not only for clinical analysis but also for Brain-Computer Interfaces (BCIs) for disabled people, for gaming, or for supervision, e.g, during driving. Here, it is important to know how many sensors are needed, and how they should be placed. This enables an easy setup of the electrode cap with reduced resources, while at the same time maintaining the system’s performance. The summarized article deals with this topic and introduces and compares several methods to choose relevant electrodes (sensors).