When someone greets you by saying, “Hi, how is it going?” they are asking you how you are doing or feeling. The phrase is a fairly common one in everyday American English. You will hear friends share the greeting, as will those who do not know each other well.
The correct response to this greeting is dependent on how you are feeling or what is going on in your life when someone asks you. To respond to this greeting, one would normally say something like, “It’s going fine” or, “I’m good, thank you.” These are appropriate responses to the question most of the time. However, if you are sick, unhappy, or going through a hard time, you might just as easily respond by saying something like, “Not great, but I’ll live.”
Although the greeting is often meant as a way of checking on someone’s well being, to make sure they are feeling good, have good health, or are doing well in life, it can also be used as an off-hand comment. For example, if you see someone you know but weren’t expecting to see, you might greet them this way as a courtesy, to start a conversation, even if you aren’t really that interested in their response.
Another example of using this phrase as an off-hand comment would be when a relative comes to visit. You might greet them with, “Hi, how’s it going?” when they walk in the door, merely to acknowledge that they have arrived or to show that you care that they are around.