If somebody, especially a stranger, opens a conversation with "How are you?", I will treat it as a greeting- a bit of an awkward greeting- but it is completely acceptable as a greeting; and therefore I will reply with a greeting- usually a customary one like "Hello" or "hi" in a friendly way. Normally this will conclude with the person and I having each others' attention and getting down to the business of whatever they wanted to discuss.
What is NOT acceptable, is when after I return the greeting, they say "How are you?" a second time. If you use that as a greeting, you can't follow up with it again as an actual question. You may use some other greeting; and then follow up with "How are you?"- that is fine. OR you can greet with "How are you?" and then rephrase the actual inquiry in a less vague way- like "are you enjoying the weather today?"; but if you say "how are you?" twice, I will treat the second one as a second greeting, and return the greeting the second time in a less friendly way.
What is NOT acceptable, is when after I return the greeting, they say "How are you?" a second time. If you use that as a greeting, you can't follow up with it again as an actual question. You may use some other greeting; and then follow up with "How are you?"- that is fine. OR you can greet with "How are you?" and then rephrase the actual inquiry in a less vague way- like "are you enjoying the weather today?"; but if you say "how are you?" twice, I will treat the second one as a second greeting, and return the greeting the second time in a less friendly way.
