American's Greeting Culture

I'm from Thailand.
Most people greet each other by smiling.
That's for stranger or informal situation.
It is very easy and simple to do so.
For people who know each other better, or have seen for a few times, or whom they older or higher position, they usually pay respect by raising and putting their palms together.
Unlike people in some other countries, they are unlikely to smile to each other.
However, it doesn't mean that they are mean.
They may do something else to greet which I don't not know.
Let me know how you guys greet people in other countries.