"어떻게 지내요?" It is used only to a person you already know each other.

You can compare English conversation with Korean conversation. A : Hey! Hello? how are you? B : I'm doing good. How about you? A : Good so far. By the way I've heard you have a new girlfriend. B : What? No, I don't! Who said that? A : 야! 안녕? 밥 먹었어? B : 먹었지. 넌? A : 좀 아까 먹었어. 근데 너 여자친구 생겼다며? B : 뭐? 아닌데! 누가 그래? Korean speakers say "밥 먹었어(요)? Did you eat your meal?" as English speakers say "How are you?". It could be weird in your culture but it's a cultural embed in Korea. I say 밥 먹었어? if the listener is younger than me or my age. If the listener is older than me, I would say 밥 먹었어요? or 식사하셨어요?(in honorific style). I'd like to skip the rest because your question was about 'how are you' in Korean.

잘 지냈어? 혹은 윗분이 말씀하신것도 되구요. 그동안 어떻게 지냈어? 뭐하고 지냈어? 오랜만이네.(정말 오랫만에 만났을때)등등...근데 한국어 읽을줄 아세요?