Most people are pretty good at these. Our parents drilled them into our heads as toddlers. They are so ingrained that they barely rate a mention in most etiquette books.
I think that thank you is the most ubiquitous. When I travel, I always make sure to learn how to say hello and thank you in any foreign language, because they pretty much cover most situations and make you sound polite. It’s also the most meaningful of the “magic” phrases. I am thanking you for something. To an extent, I think it has replaced please in a lot of situations. Instead of saying “could you do this, please?” a lot of us will say “could you do this, thanks!” How often have you signed off on an email request with “thanks!” at the end? I think this does add a nice casualness to a request and makes an email seem friendlier.
I was thinking that I almost never say please, but then I do catch myself doing it a lot at work and in situations like ordering at restaurants and other times where I want to be ultra polite. Nowadays, please seems to have taken this passive-aggressive tone, as if you should already be doing the thing this person is asking you to do. Maybe that’s because my mom always made sure “Could you please do the dishes?” sound like a command, not a polite request. Do you say please a lot? When do you use it most?
You’re welcome has fallen off the map a bit in favor of a breezy “no problem!” or “sure!” These are fine, I think, as they do convey your acknowledgement of a thanks, but a stickler for etiquette would say that by brushing off whatever someone is thanking you for, you are diminishing your own actions as unimportant. I struggle with this one a lot and have been trying to make more of an effort to say you’re welcome, but I catch myself throwing out “no problem!”s quite a bit still.