Some body language is easy to interpret: If someone sits leaning away from you, they are not interested in you. If someone has their arms crossed, they are feeling closed-off.
The easiest and most straightforward way is to find a public place where you can spend many hours relatively unnoticed, all the while observing others behaviours and interpreting what they might mean.
Our responses to others' nonverbal communication will be seen as appropriate or inappropriate as we get feedback from them. It is a process of socialization.
