It's not the same in different regions and with different people. In the first meet with a stranger, you can say"xing hui(幸会)" which means it's my honor to meet you. If he or she is a guy with reputation, you can say"jiu yang(久仰)"，which means I admire you for a long time. If he or she is familiar with you, you can say"nihao(你好)"，it is more common than"nihaoma".Also "zui jin zen m yang(最近怎么样)" "jin lai ru he(近来如何)"—how is thing going recently? are widely used. If the guy is very close to you, when see him or her,you can say"qu na ya(去哪呀)": where are you going? or “chi le ma?(吃了吗)": Have you had meal? Westerners usually think it's an offense to private. But in China, it's a way to express closeness. PS: don't worry on"吃了吗" for you don't have to treat him when saying so. Hope they would help.

Thank you for all of your replies!

you can say "hi or hello" 。。hehe..young guys also use this way ..

you can say"ni chi le ma?"

why not try "hao jiu bu jian" or "zui jin zen me yang"? these are more common greeting ways, moreover, they can show your close distance between different people.