Keep a regular sleep schedule.
This is something I completely failed to learn so far. Sure, I have some issues with procrastination or a lack of certain time-management skills, but even if I create a schedule for my whole week in advance and manage to follow it through for a couple of days at some point I completely mess it up because I sleep through half a day since I stayed up until 4AM the night before. Or I end up not getting enough sleep for several days in a row and getting sick (which happens far too often). Mostly, if I wake up at a certain time I don't get tired early enough to get a sufficient amount of sleep before I wake up at the same time on the next day (and unfortunately they don't make these time-turners yet).
It seems like every failed attempt to establish a working day routine can be mainly narrowed down to this single thing. I managed to get through High School and still get good grades even though I missed a lot of school days (due to being sick or too tired to go) because it was easy. Even at university it's still possible to pass the exams when you miss half of the lectures (although your results probably will suffer). However, I'm already afraid of my first real job.
I found that having a full-time job fixed my sleep schedule - if I have to get up, I will. Then I'll usually be tired enough to go to sleep at a reasonable time too.
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?)