In this paper we present the results of a study of human preferences in using mid-air gestures for directing other humans. Rather than contributing a specific set of gestures, we contribute a set of gesture types, which together make a set of the core actions needed to complete any of our six chosen tasks in the domain of human-to-human gestural communication without the speech channel. We observed 12 participants, cooperating to accomplish different tasks only using hand gestures to communicate. We analyzed 5,500 gestures in terms of hand usage and gesture type, using a novel classification scheme which combines three existing taxonomies in order to better capture this interaction space. Our findings indicate that, depending on the meaning of the gesture, there is preference in the usage of gesture types, such as pointing, pantomimic acting, direct manipulation, semaphoric, or iconic gestures. These results can be used as guidelines to design purely gesture driven interfaces for interactive environments and surfaces.