The main characteristic of a mobile collaborative Mixed Reality (MR) system is that augmentation of the physical environment of one user occurs through available knowledge of where the user is and what the other users are doing. Links between the physical and digital worlds are no longer static but dynamically defined by users to create a collaborative augmented environment. In this article we present generic interaction techniques for smoothly combining the physical and digital worlds of a mobile user in the context of a collaborative situation. We illustrate the generic nature of the techniques with two systems that we developed: MAGIC for archaeological fieldwork and TROC a mobile collaborative game. Keywords Mixed Reality, Mobile Computing, CSCW, Interaction Techniques