I can't presume to speak for someone else, of course, but I can address the idea of non-verbal communication. This is the part of communication which some notice, understand, and respond to intuitively while others really have to work to see it and understand it. Non-verbal communication is what we all do with our faces, arms, hands, eyes--our bodies in general--when we both speak and listen. People who are bored or uninterested tend to "fidget," for example. When angry, people often cross their arms as if to shield themselves from what is being said. (This is a self-protective stance, as well--showing defensiveness to whoever is speaking or what is being said.) Rolling eyes are often an indication of sarcasm, disrespect, or boredom.
Really, I think you probably both observe and do these kinds of things on a regular basis. (Think about what you do to express yourself when a lecture goes on too long or when a friend is obviously stretching the truth as they tell you a story or when you're listening intently.) If you aren't in the habit of noticing these kinds of things, start. If you're going to be a teacher, reading these non-verbal clues is really going to be helpful and add insight to your other observations (such as what they write or what they say). This is especially true for junior high students, who often struggle to express their true selves. It speaks well of you that you're looking ahead and asking for some advice from experienced people. Good luck with those conferences!