greeting customs

Greetings is the most important thing to communicate with someone.
A month ago,I had a chance to communicate with Western university students from places such as Harvard, Oxford, and Princeton and spend with them about a week in Komatsu, and Ishikawa as a member of the international exchange program.They taught me a lot of things about what they are learning in their university, and I introduced them about to Japanese culture. After finishing the program we have became best friends, although it's been only a week since we knew met each other for the first time. When they parted from me["When they parted from me" isn't wrong, but "When they left me" would be more common], 

I felt feeling the sorrow of parting.
I became sad. One female college student who goes to university in the US realized my emotion feelings and hugged me suddenly. I felt happy, but a little bit be surprised because I thougt hugging is the thing which is that couples do. In Japan, most people do not hug with friends .But I was understood understanding that hugging with friends is the custom of greeting in Western countries. I felt found the difference of culture between Japan and Western countries in unexpected. This surprise made me think about the custom of greetings of world countries. Since then, I have studied about the greeting cultures of each country.
While I studied about it, I found some interesting greetings.
For example, Mongolian people smells each other when they meet their friends to share nostalgia.
Tibetan people take out their tongues when they meet someone to show respect.
Kiyuku tribe people take spit to their friends. It is surprising for Westerners or Japanese people but it has the meaning of the talisman against evil in the Kiyuku tribe.
In this way, even if the customs of foreign countries looks odd, it has meaning which they put wish in.
In modern global society, it is often said of the importance to communicate with people around the world, but as globalization advances, opposition by difference of culture or
lack of understanding to another culture are increasing.
I think this opposition can be prevented by the effort that is going to understand each other .
Understanding the greeting customs of other another country is one of the most important and easiest effort to
push forward the communication with the a foreigner smoothly.
I'm just a highschool student, so I can't
solve a diplomatic issue,
but I can interchange[interchange isn't correct, but I'm not sure what is trying to be said exactly to correct] triggered by greetings.
So I want to start communication by
the greetings of the country.