History. I pay attention to any information we have on the client's possible triggers and ensure that I go into the field with an awareness of how to avoid those triggers. I also pay attention to non-verbals and cues from direct interaction with the client--things as simple as noting that I shouldn't hover over their shoulder if I'm assisting them with paperwork, for example. Body posture, proximity, and tone of voice, can all be factors that might distress a client depending on their trauma experience.