greeting someone

[Majid72]

Hi dear teachers,

When you meet someone ,which of the three following sentences do you say for greeting?
if all the tree are used ,do they mean the same thing?

-How are you?
-How are you doing?
-How are you getting along?

Thanks a lot.

[Prezbucky]

The first two are incredibly common in the US at least. The third would be understood but it's used fairly rarely (in the English-speaking environments in which I've spent most of my life: Wisconsin, Chicago, Nashville). That third example seems old-fashioned to me and, while friendly, formal nonetheless.
_________________
Billie Jean is not my lover. Hee.