Trust is a fundamental human need. It serves as an important underpinning of social interaction and collaboration, both in the interpersonal context and between man and machine. One of the cognitive factors that psychologists have defined as crucial to trust formation is predictability, that is, the occurrence of specific behavioral patterns in the expected way. With respect to human-robot interaction, this means that it is essential for the human partner to know in advance what to expect from the robot and to be able to identify its planned actions. Ideally, it should be intuitively apparent when, for example, a collaborative robot is about to intervene in a working process or in which direction a mobile robot will move next. Nevertheless, the matter of which robotic signals improve predictability for which users in which contexts still confronts research and practice with a need to gain greater insights. This talk provides examples of robot intention signals and highlights open research questions.