In this paper we discuss experiences with a collaborative and participative approach of communicating mathematics to a broad audience. We give a list of recommendations and ideas, how the public itself can be involved in creating mathematics exhibits and can become an integral part of outreach activities. The ideas are accompanied by sample activities we carried out within “IMAGINARY – open mathematics”, a project by the Mathematisches Forschungsinstitut Oberwolfach supported by the Klaus Tschira Stiftung.