顺其自然。 进行接触。 一“拥”即放。

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
While, customarily, people have greeted each other with handshakes when first introduced, these days people frequently hug on introduction without thinking twice about it.  This is more often seen among groups of friends than one friend introducing you to another friend. Use your instincts, but the best rule of thumb is that if you are offered a hug, go for it. Remember to keep the physical contact quick and light for hugging friends.  Anything more prolonged might be misinterpreted as romantic.