One standard greeting (similar to “what’s up”) is
Which is super informal, and can have responses such as the following:
- mou5 je5 (nothing)
- gae hou aa3 (quite well)
- m4 hou gong2 la (not going to speak (about it))
Lastly, if you want to be a little more serious (I actually want to know how you are), but still quite informal, you can just add nei5 (you) in front.
P.S. I ‘m not sure of the jyutping here, will come back and correct).