The truth is you don't really need to say hello when you're traveling around. But, alas, it's a nice courtesy that will prevent you from walking past people coldly. When was the last time a "hello" brightened up your day?
French: Bonjour (this can also mean "good day") / Salut (informal)
Spanish: ¡Hola!
Mandarin: 你好. [Pinyin: nĭ hăo]*
English: ...You're reading this, aren't you?
We're currently working on bringing audio to this reoccurring language primer, which focuses on useful phrases. Until then, Google Translate can help with pronunciation.