I don't remember the exact reference on HN but there was a similar discussion on Quora which you might find useful. http://www.quora.com/Etiquette/How-do-you-p

I don't remember the exact reference on HN but there was a similar discussion on Quora which you might find useful. http://www.quora.com/Etiquette/How-do-you-politely-turn-down-someone-who-wants-to-grab-coffee-sometime http://www.quora.com/Etiquette/How-do-you-politely-turn-down...