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?)
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 in common - you're at the same university. It is likely to be okay to strike up a conversation.
They're waiting for something. In a queue or waiting for public transport etc - may be bored
They're having a cigarette - they probably have time for a quick chat and if you smoke too there's a kind of unspoken thing with smokers where they will have a chat
Presence of alcohol but not a restaurant
Bad signs: Person is wearing headphones or reading - they are busy and unlikely to want to talk
They are a woman under 40-ish and you are a dude: potential difficulties, see below.
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So there is a thing with a guy approaching a strange woman - she is likely to inductively infer that you are not just after a friendly chat. The best thing to do is use caution and watch for signals that she doesn't want to be approached and be ready to back off if your intentions are misinterpreted. A good thing to do here is to make sure that it is immediately obvious that you are talking about something that is not her - comment on your shared situation ahead of saying anything like 'hello' or 'how you doing'. Commenting on the books or the museum exhibit or something like that lets her know that you're looking at that, not her tits.