As the frontiers and futures of work evolve, humans and machines will begin to share a more cooperative working space where collaboration occurs freely amongst the constituent members. To this end, it is then necessary to determine how information should flow amongst team members to allow for the efficient sharing and accurate interpretation of information between humans and machines. Shared situation awareness (SSA), the degree to which individuals can access and interpret information from sources other than themselves, is a useful framework from which to build design guidelines for the aforementioned information exchange. In this work, we present initial Augmented/virtual reality (AR/VR) design principles for shared situation awareness that can help designers both (1) design efficacious interfaces based on these fundamental principles, and (2) evaluate the effectiveness of candidate interface designs based on measurement tools we created via a scoping literature review. This work achieves these goals with focused studies that 1) show the importance of SSA in augmented reality-supported tasks, 2) describe design guidelines and measurement tools necessary to support SSA, and 3) validate the guidelines and measurement tools with a targeted user study that employs an SSA-derived AR interface to confirm the guidelines distilled from the literature review. / Doctor of Philosophy / As the way in which humans work and play changes, people and machines will need to work together in shared spaces where team members rely on one another to complete goals. To make this interaction happen in ways that benefit both humans and machines, we will need to figure out the best way for information to flow between team members, including both humans and machines. Shared situation awareness (SSA) is a helpful concept that allows us to understand how people can get and understand information from sources other than themselves. In this research, we present some basic ideas for designing augmented reality (AR) tools that help people work together in better ways using SSA as a guiding framework. These ideas can help designers (1) create AR tools that work well based on these basic ideas and (2) test how well different interface designs work using specially developed tools we made. We completed user studies to (1) show how important SSA is when using AR to help with tasks, (2) explain the design ideas and tools needed to support SSA, and (3) test these ideas and tools with a study that uses an AR tool, based on SSA, to make sure the guidelines we got from reading other research are correct.