It would depend on your relationship with the asker. Americans use "how are you" as a general greeting so sometimes they just mean "hello" and nothing else. If you're not close to the person, even if you're doing terrible, you would still just answer "fine" and move on. My boss used to say "Hi, Wei. How are you?" to me all the time when he passed by my office and doesn't even slow down to hear my answer. But if it's your close friend who asks and you would like to continue the conversation, I guess you would just start the conversation how you usually do: by bringing up a topic you're both interested in. You can segue into the conversation by using "by the way." So you can say, "I'm doing good. By the way, have you seen the latest episode of [insert TV show you both watch]?" TV shows, movies, sports, restaurant recommendations are usually pretty good conversation starters. Office gossip is always interesting for women; I know it's frowned upon, but that's the reality of office dynamics.

Hello Kana, "How are you?" is a polite opening in a conversation. Similar to the formalities you have in Japanese. There is no need to reply in detail usually "I'm fine" or "I'm good" + "thank you" is enough. There are a few other short possibilities but these are the main two. Whatever you do please do not start talking about your health, job or anything else in detail at this stage. The other person will probably switch off. Hope this helps Bob PS Your question should be "How can I answer it?"

Hi, Sounds like you already know what to say. Here are a few more ideas: "Fine, thanks. how are you?" "Great. You?" "Good. You?" The last 2 would be for friends because they are so short. "Living the dream" is a humorous way to respond, too. As you probably have already figured out. "How are you in US English is a way to say "Hi." People do not want a blow-by-blow of how you are really doing. If someone really does want a detailed description of how your life is going, they will ask, "So, tell me, how are things? How are you doing, really?" And when they ask this, it will probably be in a situation where you 2 can talk unhindered, say, in a restaurant as you share a meal, in a bar having a drink, at McDonald's, not in passing in the hallway at work.