To ensure your future notes are useful to you, read what you have already written weeks or months (or more!) ago. Initially, I found my writing was too sparse. Too much context stayed in my head and my notes were almost useless. I reviewed them just before I completely forgot the context and updated them. The feedback loop of reading my own writing has helped me improve a lot at writing well for future me. I have to write to myself as if I will be an amnesiac in the future.
As for finding my writing when and where I need it, I try to give every file a unique and memorable title so I can refer to it in other notes and writings I access more frequently. For me, this means linking to notes and thoughts in Obsidian and creating aliases. If I know I wrote something down, but think the title is "Note B", but the title is "Note A", when I find Note A, I will add an alias with an additional title or keyword so that in the future, searching for Note B will surface Note A (and Note B, if it exists). Or, I will add a link to Note from the 1 or more of the most topically relevant note.
P.S. This maintenance doesn't take me much time. I only do it if I notice that a note was harder to find than it should have been and it usually only takes a few seconds to make sure it's easier next time.
(I used to use OneNote and Evernote, but bi-directional links with auto-suggest and a file quickswitcher are such gamechangers.
I was there when Obsidian and Roam Research felt like the first two options doing this seriously. The ecosystem has grown up around me and I love it. But you can do this with loads of other tools now.)
My filenames generally follow a "YYYY_MM_DD_HHmm Descriptive Title, perhaps a thesis statement - Source, if applicable" format.