Cultural Differences

When we are studying other cultures or interacting with people of another culture, we understand that all cultures have not only some similarities, but also some differences. I came in America from Russia and I believe that in USA we can meet people from almost every country in the world, that is a big opportunity in learning about other cultures. I would like to speak about some cultural differences.
For example, in Russia when you speak with someone and you nod, it is mean that you are agree with your interlocutor and in opposite when you are disagree with your interlocutor you shake your head. In United States I meet some Bulgarian friend and I was surprised, when he told me that in Bulgaria when you nod, it is mean that you are disagree with your interlocutor, and when you shake your head, it is mean that you are agree with your interlocutor.
In Russia the highest score in school is five and the lowest score is one. In Germany the highest score in school is one and the lowest score is five.
I also found some cultural differences between Russia in United States. In Russia married people wear wedding ring on the left hand and in United States married people wear wedding ring on the right hand. In United States of America on holidays people give to each other even quantity of flowers, but in Russia people give even quantity of flowers only to dead people.