你好
你好 is the most common Chinese greeting, equivalent to "hello." It is appropriate in both formal and informal situations when meeting someone. It literally means "you good" and can be used at any time of day.
你好,请问这里是图书馆吗?
Nǐ hǎo, qǐngwèn zhèlǐ shì túshūguǎn ma?
Hello, excuse me, is this the library?
你好,我是新来的同事,叫小明。
Nǐ hǎo, wǒ shì xīn lái de tóngshì, jiào Xiǎo Míng.
Hello, I'm a new colleague; my name is Xiao Ming.
你好,好久不见,最近怎么样?
Nǐ hǎo, hǎojiǔ bújiàn, zuìjìn zěnmeyàng?
Hello, long time no see. How have you been lately?