你好 - is your go to greeting for almost all situations. When in doubt, say 你好 (unless you're like talking to the president). This is translated as "hello/hi/hey", but it really means "Hello/hi/hey, how are you?". When somebody says "你好" to you, you should really respond by saying"很好，谢谢！" (or however you are feeling that day, but like in English, if somebody says anything other than "I'm fine", you aren't really interested, are you?). You should note that people don't actually say 你好吗？, so to avoid sounding like a foreigner, don't say it. When you answer the phone, you say 喂. This is written as wèi, but when you say this when you answer the phone, it pronounced wéi, always! If you want to holler at someone to get their attention (probably with the intention of beckoning them over), then you can shout 喂！at them, but this time is wèi in the fourth tone. After you say 喂 on the phone, or somebody says it to you, then next thing you'll probably hear is 你好, to which you should reply 很好，谢谢（你）. 嘿！- This is northern and more of an interjection, but I have seen people use this as "hello"/"hey" I have read 哈罗/哈啰 in books before, but I've never heard anybody say it in real life. I believe it's a transliteration of "hello" from English. 你去哪儿？- Where are you going? This can also be used as like "'sup?, what cha doin'?" 你在干嘛？- What are you doing? Again, a little like "what's up". I used to work in a big tourist attraction with lots of Chinese visitors. I always greeted them in one of the following ways: 劳驾，你（们）是从哪儿来的？ 请问，你（们）是从哪儿来的？ 请问 (literally "please ask"), is your go to translation for "excuse me". As far as I know, 劳驾 is more of a Beijing thing. You can also say 打扰（你）一下, which means something like "I'm sorry to disturb you, but...". These never caused issues, unless I was talking to Taiwanese people who cringed at the "儿". If you want to be safe then just say 哪里 instead.

嗨，好久不见~ 嗨，最近变帅了啊~ 嗨，最近过得怎样啊~ And so on..

同事早上上班一见面，可能只会说一个”早！“。熟人是上见面也可以只说”早！”，据说广东人说成“早晨！”

英语有多少种问候方式，汉语也基本上都有。现在的英语书中，把hello, hi, how are you? how are you doing?等等各种说法都译成“你好”。这是不对的。比如： 最近可好？ 身体还好吧？ 最近忙什么呢？ 一切都好吧？ 家里都好吧？ 好久不见了！ …… 这里面也要分成关系的好坏、亲疏等等。 顺便说一下，象”嗨、嘿、喂“这些在过去的古人、包括现在的一些老人看来，都是不礼貌的打招呼方式。只是现在的年青人都不再意了，但用于长辈、上级，一样是不礼貌的。 真的要按过去的中国式的寒暄方式（打招呼）礼节是非常多的，很讲究的，见什么人要说什么话。现在的人都不讲究这些了。