In learning to read body language, it helps to know the Big Four, that is, four major categories of movements. Each one gives you some information about a person's emotion and intent.
The Big Four in body language are:
Illustrators punctuate what you're saying so they could be intentional or unintentional. You may automatically use your arms, torso, head, legs, and everything else to accent what you're saying. Sure, sometimes you might rehearse your movements if you're giving a presentation at a meeting, but in normal conversation, you don't deliberately choose every move you make. Everyone has a baseline style of using illustrators. When you deviate from that, it's a signal that there's a shift in the intensity of your emotions.
Regulators are movements and sounds to control another person's speech. Again, they could be intentional or unintentional. The postures and movements associated with active listening encourage the other person to keep talking. In contrast, when you clamp your lips while someone is talking, you are sending the signal that you don't want to hear any more or you don't want to hear more of the same. When you turn away slightly, it's the same kind of signal.
Barriers can help you establish personal space. They can be a body part, like an arm or a shoulder-the proverbial "cold shoulder"-or an object like a cell phone or table. They can make you look weak and afraid-like you have to hide behind something in order to have a conversation. On the flip side, when you sit behind your big desk and the person you're talking with is sitting on the other side of it, that barrier conveys the sense that you have a lot of personal real estate.
Adaptors are nervous movements that are self-soothing in nature. They might be grooming gestures, like brushing a piece of lint off your jacket even though there may be no lint there, or straightening a tie, or playing with your earrings or hair. They could be rubbing two fingers together. The use of adaptors is one of the clues of possible deception. Most people are not skilled at any level of deception, whether it's omitting a fact, distorting a fact, or embellishing a fact. Engaging in deception, even if it's minor, will probably cause some stress and that stress will leak out in the form of an adaptor.