I'm a big believer in using simple index cards for this sort of thing. But there are modern alternatives also.
For the traditional approach, make a card for each paper. It contains title and author as well as publisher/source. It also contains a one or two sentence summary of the paper. What is the reason that this paper is important/interesting?
Cards are kept in a file box, perhaps in author order.
The advantage of this approach is that your card deck will still be available to you in fifty years after multiple operating systems and software systems have become extinct. Paper lasts. Another advantage of index cards is that they are small so you can only write essential things.
As a supplement, you can keep a notebook with a page or two for each paper. The index cards contain a page reference into your notebook system.
But the disadvantage is that such a paper-only system is hard to search. So you might consider an alternative. There is software for "digital index cards" that let you do the above on a computer and provide the opportunity for both searching and for updating the formats and organization of your notes. This might be a better solution for you in general, but don't overlook the permanence of paper. If you are really serious, use such a software system but also use a printer that conveniently and efficiently prints real index cards. Now you have your bomb-proof backup that you will be able to refer to in your 70's in the post-computer era.
Personal note: I have, in fact saved such things as my college course notes from deep into the previous century and have, very occasionally, gone back to refer to them. Later, I kept things on floppy disks that I can no longer access, even though I have the equipment to do so. They degrade as paper does not. Provided you use fairly good paper, of course. I found my first "paper" done back in secondary school (on paper, obviously, created when computers were made of vacuum tubes) and found it "interesting". Since it was typed (on a typewriter), I can scan it for more modern use.