What do you mean when you ask "How are you?"
I have been asked one simple question many times by Americans: "How are you?". I know this does not mean that the person I am talking to wants to know how I feel, but sometimes I see that they repeat the question to me, so I answer that "I am fine", and I do not know what I should answer other than "fine" to people who I do know.
I know, for example, that in Hebrew "How are you?" in most cases means "Hello". In Russian if you ask "How are you?" you definitely want to know it.
What do you mean when you ask this question? What answer do you want to hear?
Solution 1:
Context is key. That being said, in most cases, in American English at least, "How are you?" just means "Hello." Not even a formal "fine" response is required. It would not be uncommon to hear two Americans have this conversation:
Joe, how are you?
Nate, how are you doing?
or
Joe how are you?
Nate, good to see you.
If you want to respond to "how are you" by telling about your condition, you can, but it needs to be a very short response.
Joe, how are you?
Not bad, how about you?
Oh, you know. Sick of all this snow.
or
Joe, how are you?
Doin' great. I closed the Smith deal.
No kidding?
The person asking "How are you?" is not trying to probe the depths of your health or your psyche; he or she is just making polite conversation. If they really want to know something, they will say something along the lines of:
I haven't seen you in ages. What have you been up to?
or
I heard about your husband. How are you holding up?
Solution 2:
It depends on who asks the question. In casual conversation, people expect the response: "Fine, how are you?"
If a doctor asks you the question, he expects the truth.
Solution 3:
The answer to this question would vary in different situations. In most cases you should reply with neutral:
"Fine. What about you?"
"Great! How are you?"
Even if you had a really bad day, when you have a business meeting, you wouldn't answer something like this to the question you mentioned:
"Oh, I had a really bad day..."
"Bad, what about you?"
On the other hand, if you are talking to your close friend, this is acceptable.
And, as @Gary's Student mentioned, sometimes this question is not just for the sake of politeness, but it is a direct information request (a visit to a doctor).
Solution 4:
It is just a conventional way to exchange the first introductory words when you meet someone. The idea is to create a positive contact with the other person showing interest in his respect. But it is sort of fixed expression which has lost its literal meaning and has evolved into a sort of stereotype. So, don't worry about the meaning and just say: I am fine. Thank you, and you?