I solved this (particularily painful southern US) problem by interchanging. Rude children have been known to just "dissappear" in the rural south...
"yes, please" if I am pleased to be asked because I am very thirsty.
"yes, thank you" if tea is being passed and every human (or other human) is partaking in the tribal "drink together" ritual.
"no, but thanks so much for asking" if I am not thirsty (and/or couldn't balance a cup and saucer and conversation).
No one has seemed upset, or called me for being rude...puzzled but not upset (and well, the puzzling is icing).

When I was younger I never said things like please and thankyou enough. Or called people sir and ma'am. My parents were always upset with me but i never really saw the need.
Now I've learned when to add those little things (though i'm still not comfortable with "yes sir/ma'am") and don't really think about it. I find it's best to just do it. Makes things easier. It's just something that people expect and you get weird looks when you don't.
erkolos you're lucky not to have these little niceties. What sort of thing do they say in Norway to make things more polite(or not)? Anything?
Please don't stop saying "yes please" and "no thank you."
Here in jacksonville there is much hatred for one another.
It all started with stopping the ma'am and sir.
Then went the please and thank you.
Then yes and no were replaced with yeh and nah.
Then there was no respect for yourself.
Then no respect for anyone or anything.
Then went the conscience.
Now people kill each other and don't care.
They blame everyone else.
I'm old enough to remember a better time.
A time of innocense(sp?) that can never be replaced.
A time when you didn't have to lock your doors.
A time when you could safely take a walk at night to feel the cool breeze.
A time when everyone took care of each other.
A time when you lovingly critized one another.
A time when you could speak your mind.
Now you can not do ANY of that.
There is nothing but distrust of everyone.
You can not critisize because it might "offend" someone.
Never mind if you are actually right.
I'm saddened and miss/crave the "yes ma'ams" and "no sirs."
Please don't stop!
I love you.
Annie
I usually say either "yes, thank you." or "sure, thanks." But if you are at Tim Horton's or other coffee joint you shouldn't have to, but I see people doing it all the time. I've even done it. "Hi, may I please have an extra large hot chocolate and..."