How is it going?

"How is it going?" — це таке собі частовживане неофіційне вітання, яке можна перекласти як "Як ся маєте?". Як відповідати на це вітання знайшов тут.

Ось пара цитат звідти:

If someone asks you, "How's it going?"

Your answer can be very short:

"Fine. You?"
"Great. You?"
"Terrific. You?"
"So-so. You?"
"Pretty well. And you?"

* * *

It can very much depend on the context. Who is asking, and what their relationship to you is.

When a grocery store clerk asks you as you're checking out, it is frequently just a formality. Depending on how I'm feeling at the time, I might acknowledge the question, but not ask a question in return...

"Fine, thanks."
"Very well, thanks."

Or if I'm feeling more loquatious and/or more outgoing (and I usually do), I might say...
"It's going very well. How about you?"

I have to admit that clerks are more likely to say "How are you?" than "How is it going?" But there are probably other situations where you can omit a return question.