Perhaps I should further specify just what sort of spaces I'm clear and unclear on. (All "maybe"s, "probably"s refer to my own uncertainty, of course - for simplicity I'm doing writing this as if I hadn't read any of the cousin posts yet.) The examples listed here are whatever I think of, mostly relevant ones but not all - I don't think there's a zoo anywhere around here and I haven't been to one in quite some time, but the example occurred to me while I was writing this so I threw it in. I expect I'm right about the things I'm certain of but should that not be the case corrections would be appreciated!
Definitely OK to approach people: "Private public spaces" - anywhere where a person you don't know can be assumed to be a friend of a friend - small parties, common rooms in dorms or co-op houses
OK to join existing conversations, maybe not OK to approach people initially: "Purposed public spaces" - anywhere where a person you don't know can be assumed to share a common interest - a common room in a school department building, e.g. Game stores probably fit here too. Also probably competitions of any sort.
Probably OK but currently avoided by me: Outside - on the street, on the quad, in the park. Here the location doesn't let you infer much of anything. (Unless something unusual is occurring, then clearly OK as people gather around it.)
???: Fast-food places or food courts. Non-quiet spaces where people go to get work done (but which are too general to fall under #2.) Zoos, museums, other similar places. Bookstores.
Probably not OK: Libraries.
Definitely not OK: Anywhere where you shouldn't be talking in the first place. Most restaurants.
Again, thanks! The sibling posts have already clarified things some.
In ambiguous environments, it is best to determine ok-ness on the basis of the people.
Good situations: You are both doing the same thing - looking at the same genre of books in a bookstore, the same exhibit in a museum or zoo, both walking dogs in a park etc. This makes it easier to talk as you already have one thing in common and you can comment on that to see if they are receptive to conversation.
Something unusual happens - a delay on public transport, something wacky is going on in the quad etc
If you mean quad as in university, you already have a thing...
I am beginning to suspect that it is surprisingly common for intelligent, competent adults to somehow make it through the world for a few decades while missing some ordinary skill, like mailing a physical letter, folding a fitted sheet, depositing a check, or reading a bus schedule. Since these tasks are often presented atomically - or, worse, embedded implicitly into other instructions - and it is often possible to get around the need for them, this ignorance is not self-correcting. One can Google "how to deposit a check" and similar phrases, but the sorts of instructions that crop up are often misleading, rely on entangled and potentially similarly-deficient knowledge to be understandable, or are not so much instructions as they are tips and tricks and warnings for people who already know the basic procedure. Asking other people is more effective because they can respond to requests for clarification (and physically pointing at stuff is useful too), but embarrassing, since lacking these skills as an adult is stigmatized. (They are rarely even considered skills by people who have had them for a while.)
This seems like a bad situation. And - if I am correct and gaps like these are common - then it is something of a collective action problem to handle gap-filling without undue social drama. Supposedly, we're good at collective action problems, us rationalists, right? So I propose a thread for the purpose here, with the stipulation that all replies to gap announcements are to be constructive attempts at conveying the relevant procedural knowledge. No asking "how did you manage to be X years old without knowing that?" - if the gap-haver wishes to volunteer the information, that is fine, but asking is to be considered poor form.
(And yes, I have one. It's this: how in the world do people go about the supposedly atomic action of investing in the stock market? Here I am, sitting at my computer, and suppose I want a share of Apple - there isn't a button that says "Buy Our Stock" on their website. There goes my one idea. Where do I go and what do I do there?)