Eye Contact
In the United States, most people consider it polite, and a demonstration of sincerity, to look each other directly in the eye, at least in intervals, when having a conversation. It is considered very rude and in some cases may be interpreted as threatening to look continuously at someone or stare at someone unless you are engaged in conversation with that person. It is as rude to stare or comment about someone's body in America as it is anywhere else.