I hear from people greet saying "howdy". I guess that is short form of how do you do. I normally reply that "I am good and how are you doing?". Is there cultural specific reply that would give more appropriate meaning and value to the person who greeted first? I mean that instead replying just "I am good", would it be more value to reply "howdy" again?
Since there is no texan.stackexchange.com I'll address this here question here.
Howdy! can be replied to with just a nod and a smile. It simply means "Hi!" in Texan - not "How are you doing?".
Or you might reply, "Hey Y'all Doon?" if you want to engage in proper Texan interactions.
Replying in proper English, well pronounced, with each syllable clearly spoken, is HIGHLY discouraged.
Better, "Whazzup!" than "What are you up to?"
Better, "Mornin!", "Afternoon!", or "Evenin!" than "good morning", "good afternoon", or "good evening".
Responding with an answer to how you are doing is 100% counter-indicated - better to simply say "Greetings!" than to confuse the Texan in front of you with the answer to a question they did not ask.
Depends where you are, although the few places I know of that use "Howdy" are places where those that say it do not expect a literal answer, I have heard it answered as if they did on occasion.
There is similar phenomenon between Irish english and British english with the phrase "How are you" or "how're ya" as its more commonly pronounced. In Britain it can start a full conversation on a persons various ailments whereas in Ireland it would be very unexpected to answer it with anything other than another "how're ya"