That isn't "simple". Let's say your preference is "I don't want to talk to this person." That cannot be said politely! Notice instead to make it polite you h

That isn't "simple". Let's say your preference is "I don't want to talk to this person." That cannot be said politely! Notice instead to make it polite you had to recast it -- "I would rather be doing X rather than talking to this person." That is not an obvious transformation, and it's not helpful to go around saying that it's "simple". Instead you could give explicitly the advice that you've given implicitly: Take your preference not to talk to the person, and recast it as a desire to do X (where X doesn't include talking to the person). Now, you may point out that these two preferences are extensionally equivalent. But we're working with mental representations here, so the distinction is important. Also, this approach is not bulletproof. E.g.: You're not doing anything but watching the walls of the subway tunnel go by. "Sorry, I'm trying to...?" This leaves you with a lack of things to say. It also has the general problem of excuse-making (because that is what you are doing when you recast your preferences like that), namely, the person may try to engage you along those lines. ("I'm trying to solve this puzzle." "Oh, yeah? What sort of puzzle is it?" Sure, there's are potential replies to that (e.g. "It's a masyu puzzle, but please leave me alone." or "It would take too long to explain, sorry".) My point is it is not as simple as "just politely communicate your feelings, preferences/and or needs", often because doing so is impossible without violating other social constraints. (Notice how "It's a masyu puzzle, but please leave me alone" is more explicit and less polite in its "go away" -- but this is OK in this context because you've already told the person to leave you alone once. These sorts of things have to be accounted for.)