KoreanClass101.com:
When you drink, you should not fill someone else’s glass until it’s empty.
Turn your head so your boss (or anyone older) won’t have to watch you drinking. This only applies in formal situations, usually your boss will ask you to be more comfortable (though many still turn their head, because it’s considered polite to still do it once you get permission not to). You know, now that I think of it, you see the main character of 엽기적인 그녀 do this when he drinks with his girlfriend’s dad.
It’s not just for the boss, you’re generally supposed to turn your head for anyone older than you. Even if you tell someone younger it’s ok, they’ll still turn their head.
thanks, I changed the text to reflect that.