What's more basic than saying hello? If nothing else, wouldn't it be nice to greet one in their native language prior to saying "Do you speak English?" In the Korean language, there are three ways, and scenarios for saying "hello." The formal, informal, and phone greeting. The formal is: Ahn nyeong ha se yo [안녕하세요] = "Hello" (pronounced ahn-yan-ha-say-yo)
The informal is: Ahn nyeong [안녕] = "Hello" (pronounced ahn-yan) I believe this can also be used for goodbye.
And for the phone: Yeboseyo [여보세요] = "Hello" (pronounced yaw-bo-say-yo)
Next up is either "thank you" or situational-based "goodbye."