There are a couple of core concepts, and they’re so simple you’ll wonder why you haven’t thought of them before.
It’s worth mentioning at this point that all of this is free, and it’s possible to implement it without any additional tools.
I was introduced to the Johnny Decimal filing system by @jack. I’m going to give a go with my own computer document filing. As organised as I think I am, I certainly struggle to find digital files on a more regular basis than I would like.