How do you say hello to someone you know? Do you smile? Do you touch the other person? Actually, people from different (文化) greet each other differently. There are various ways of greetings in this globe. Here are some interesting ways, which (也许) be useful for you.
In China, many people (握手) their hands when they meet. Sometimes they just smile and say "ni hao", something like "Hello" or "Hi". While in Japan, people often bow their heads to show (尊重). In India, Nepal and Bangladesh, people bring their hands together in front of their heart and say "Namaste". In Malaysia, you put your hand on your heart and (点头) your head. Sometimes you also take the person's hands in your hands first.
When you greet a grandmother or grandfather or another (更老的) person in Turkey, you kiss their right hand and then place it on your forehead. They do this in the Philippines, too. The Maori people in New Zealand rub (鼻子) together when they meet. This is called "hongi". In the US and in other countries, some people like using a "fist bump" to greet another person. Both people make a fist, push their arm forward (缓慢的) and touch each other's fists.
But what if you don't know how to greet others in a (陌生的) country? Just smile! Smile is the most (强有力的) language in the world. It is also a universal language, which is widely used throughout the world.