This paper stresses the role of building trusted relations in the social Internet of Things (IoT). Building upon social networks between people and mimicking their behavior, things can participate in multiple relations such as avoid-me, work-for-me, and back-me. However, these things could be misused undermining their performance and raising conflicts that could jeopardize any IoT application. To address misuses and foster trust among things, policies in the Object Digital Rights Language (ODRL) are defined in terms of what is permitted to exercise, what is forbidden from exercising, and what must be exercised on relations between things. A system demonstrating the use of policies in building trusted relations in the social IoT is also presented in the paper.