Related: buy a small and reliable compass. Not a compass app for your phone, but an actual compass. GPS, your own spatial awareness, and reasonable assumptions about geography can all let you down, but north is always north.
Almost equivalent: Buy a lightweight and reliable spear. Not a speargun or an effective modern weapon, but an actual pointy stick. Guns, the rule of law, supermarkets and the reasonable assumptions that your geographic location contains no dangerous predators can all let you down. But a pointy stick is always a pointy stick.
This is an unfair comparison, especially in light of the explanation given in the edit.
OP's point was that GPS can frequently be unreliable. In terms of navigating without it, basic orientation is typically enough to get you started, and "smart" substitutes for a compass are strictly inferior to an actual compass.
This is an extension of a comment I made that I can't find and also a request for examples. It seems plausible that, when giving advice, many people optimize for deepness or punchiness of the advice rather than for actual practical value. There may be good reasons to do this - e.g. advice that sounds deep or punchy might be more likely to be listened to - but as a corollary, there could be valuable advice that people generally don't give because it doesn't sound deep or punchy. Let's call this boring advice.
An example that's been discussed on LW several times is "make checklists." Checklists are great. We should totally make checklists. But "make checklists" is not a deep or punchy thing to say. Other examples include "google things" and "exercise."
I would like people to use this thread to post other examples of boring advice. If you can, provide evidence and/or a plausible argument that your boring advice actually is useful, but I would prefer that you err on the side of boring but not necessarily useful in the name of more thoroughly searching a plausibly under-searched part of advicespace.
Upvotes on advice posted in this thread should be based on your estimate of the usefulness of the advice; in particular, please do not vote up advice just because it sounds deep or punchy.