你好，很高兴能回答你的问题。首先，hello 在中文就是你好的意思。If you just wanna know how to say ’hello’ in Chinese, you can just say’你好’, it can be used in almost any situation. But if you are on some more formal occasions, you may need to say’您好’ to show more politeness. You can also say’嗨’to your friends, or’哈喽’(from English ’hello’), they're very informal and causal words, don't say them to your boss, elderly people or someone you don't even know. ’再见’ and’拜拜’both mean’good bye’ in Chinese, ’拜拜’is more common in daily conversation and as far as I know, you can say’拜拜’to everybody you know, it's an informal word though.

According to different people and different situations, u can use different ways to express greeting or farewells in Chinese. For example, in usual life, 你好 is the most common when u meet strangers. When u meet someone that u wanna show respect to, you'd better use "您好" In less formal spoken Chinese, u could also say "Hi" written in Madarin is "嗨" And more examples: What's up? How's the life? How is it going?The three are similar with "最近怎么样" "最近还好吗" Long time no see :好久不见 To express goodbye, u could say "再见or拜拜or 下回见，回见，回头见(see you next time)

教导这个词比较正式，一般用于老师对学生，用指导或指点比较合适。 是“请指导我汉语”，但这样说很生硬，应该说： 请各位指导一下我的汉语 或者 我想请教各位一些汉语问题 问候的话分不同情况： 对于长辈及上级：如老师，你就要说，x老师/x科长，您好(x表示姓氏) 对于陌生人：您好或者你好(前者语气比较客气) 对于朋友：嗨、干嘛去呀、最近在忙什么呀 都可以表示问候

其实“你好”可以经常用，如果遇到长辈，一般说“您好”，但在南方的话一般“你好”就足够了。