Ask HN: How do you store your lifelong learnings for your future self?

Often as I'm learning, exploring, researching or chatting to people I come across information which I believe will be useful to me at some point in the future, but is not relevant right now. (Simple example: good job-hunting advice when you aren't job-hunting).

How do I effectively store and catalogue this information so that when, in the future, it suddenly becomes relevant, I can pick up on this wealth of information that past-me has stored.

I'm interested in hearing both about broad approaches, as well as specific tools and methods which you use.