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?)
Regarding investment, my suggestion (if you work in the US) is to open a basic (because it doesn't periodically charge you fees) E*TRADE account here. They will provide an interface for buying and selling shares of stocks and various other things (ETFs and such; I mention stocks and ETFs because those are the only things I've tried doing anything with). They will charge you $10 for every transaction you make, so unless you're going to be (or become) active/clever enough to make it worthwhile, it makes sense not to trade too frequently.
EDIT: These guys appear to charge less, though they also deal in fewer things (e.g. no bonds).
Scottrade is another well known company that provides the same services. They only charge $7 dollars per transaction (more more for penny stocks). I've had very positive experience with them.
One thing to keep in mind is that doing stock trading will make your taxes more complicated and more expensive to fill out.