Reading Students

In our profession, it is safe to assume that many of us are better as reading texts than we are at reading people. The job of non-directive tutoring, however, requires exactly that. A tutor must be alert for signs of anxiety, frustration, surprise, and happiness in clients, yet I believe few of us are taught exactly what these emotions look like.
The reason for this is simple: diversity. In a tutoring environment populated by students of different races, it seems

Are there universal patterns in nonverbal communication?
What are they?
Is it possible to use these patterns to read students?

Is reading students ethical?
Do tutors already do this, consciously or unconsciously?
Does reading students offer potential benefits to tutors?
Can tutors read students accurately without training?
Can tutors be trained to read students accurately? What kind of training might help?
What happens when a tutor is trying to read someone from another culture?