How do you greet!!!!

I never find any where else like international office where it has a lot of friends who are from very many countries as Korean, Japan, Turkey, Saudi Arabia,Hong Kong, Thailan, ect. Each country will has one culture and whether it is similar to Viet Nam or not. you know I have met and learnt from them many thing such as how to greeting in Thailan; they put their hands together and make a palm to greeting each other, in korea my friends greet their friends by say An-nyung-ha-se-yo. If they greet older people the way to greet is more formal, they have to bow, deep bow not just a lillte. However, in Saudi Arabia my friends hug, put their cheek together and kiss the air. they do on both side of thier face. Hmm, it does not happen in Viet Nam, people in Viet Nam more informal, they just say hi and if we are really close we do not need to say hi we just padding on shoulder, and ask " how are you?" which is common question in the US. Kissing in Viet Nam which is means a woman and a man have a especial relationship, or just for mother kiss her children. Vietnamese don't use kissing to greet each other as same as Mexico. In Mexico, it have to be one kiss on the cheek but kiss in the air. In some countries aslo kissing for greeting like Mexoco is French, Italia.
The most common greeting in the world is shaking hands. Shaking hand is really popular in many countries especially in business. it makes business man look pro ^^. it is a classical way but it is not backward lagging behind.