How to be a guest in the famoly of America?

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Recently,I'm making a project about some information of America,such as how the americans greet people? Kissing ,huging,shaking hands or just a smile? In what situation,they may kiss each other,and kiss where? Another question I'm confused is that how to be a guest in America? Is it necessary to buy a gift or a bunch of flower? And what kinds of gestures do the americans often do? I'll appreciate you much if you can tell me some about it~~~ Thanks~~~