When To Say 'Thank You'

One should only thank someone when that person expects to be thanked. But in many cases, one can only guess what the person expects and in these situations, the following rule will do a lot of good:

I would suggest that the words 'thank you' should only be used when you want to express your gratitude to someone for either going out of the way to help you or helping you on your request or helping you when you did not expect it.

In all other cases, 'thank you' has a counter-productive effect.