I once had a student who told me she liked how I sat next to her rather than behind her, like her last teacher did. She had wondered if he was really listening all the time back there.
Occasionally, I will move in closer to my students, especially when I get the sense they are not focusing 100%. Right or wrong, I feel like my concentration on the task at hand will activate their concentration.
When I feel like I have said about all I can say on a piece and am ready to turn over complete ownership of a piece to the student, I'll have them play it for me while I just sit back from a distance and listen. Sometimes, I want them to forget I am there and not worry about what I'm going to say when they are done, but rather just let me hear it as if they were playing it at home. Sometimes, students have actually confessed to trying to change their playing in the lesson, to align with what they think I want to hear. I feel terrible when that happens.