你是售货员？你是顾客？不了解。very good, just so so. as usual, like always.简单的可以这么回答吧。

售货员的话，你可以回答，可以不回答，可以反问回去。

如实回答

1.
- How's it going, man.
- Hey, what's up. Blah blah...
2.
- How's it going?
- Fine, thanks. What about you? (或类似的话)
3.
- Hey, how's it going?
- Blah blah....

good good, how about you?---that's what i usually say.