Follow-up to: Boring Advice Repository
Many practical problems in instrumental rationality appear to be wide open. Two I've been annoyed by recently are "what should I eat?" and "how should I exercise?" However, some appear to be more or less solved. For example, various mnemonic techniques like memory palaces, along with spaced repetition, seem to more or less solve the problem of memorization.
I would like people to use this thread to post other examples of solved problems in instrumental rationality. I'm pretty sure you all collectively know good examples; there's a comment I can't find from a user who said something like "taking a flattering photograph of yourself is a solved problem," and it's likely that there are other useful examples like this that aren't common knowledge. Err on the side of posting solutions which may not be universal but are still likely to be helpful to many people.
(This thread is allowed to not be boring! Go wild!)
I'm heartened that your comment is so well-liked. I made the same point a year or two ago and got back a bunch of nonsense about how the second law of thermodynamics cannot be violated.
It's interesting that the second law of thermodynamics is what people use here. As long as your metric is losing weight, the relevant physical law is conservation of mass, and starting from conservation of mass helps clarify the issue enormously, I think. (Apparently the mechanism by which burning calories actually causes you to lose weight is exhalation of carbon dioxide. I feel like I knew this once, but forgot and only very recently relearned it.)