I am usually pretty cordial and answer something like "I do some things well and others great... and you?"
When I was in China it wasn't too uncommon to have little children run up and ask "And how are you today sir?" Then they would be overcome by shyness and run away before I could respond. This usually happened when there was a crowd.
If they didn't run away I would drop down on one knee to be at their height and tell them "I am very well, y nehow ma? (How are you in Chinese). That always brought on a flood of laughter... then they would run away... lol.