Our future will likely be reshaped by Mixed Reality (MR) offering boundless display space while preserving the context of real-world surroundings. However, to fully leverage the spatial capabilities of MR technology, a better understanding of how and where to place virtual content like documents is required, particularly considering the situated context. I aim to explore spatial organization strategies for virtual content in MR environments. For that, we conducted empirical studies investigating users' strategies for document layout and placement and examined two real-world factors: physical environments and people present. With this knowledge, we proposed a mixed-reality approach for the in-situ exploration and analysis of human movement data utilizing physical objects in the original space as referents. My next steps include exploring arrangement strategies, designing techniques empowering spatial organization, and extending understandings for multi-user scenarios. My dissertation will enrich the immersive interface repertoire and contribute to the design of future MR systems.