How to reply to
Good day, sir
in the beginning of the conversation as a greeting?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
This is more a question of etiquette and personal style than language. It's polite to acknowledge the greeting somehow. A simple "Hello" is sufficient. If you do wish to engage in conversation, then add a question or a bit of small talk. Examples:
Hello, how are you?
Good morning. Lovely day, isn't it?
Hi, Bob, how's the wife and kids?