* Whenever I come across an interesting project hosted on Github (On Hacker News, Mastodon or some such place), I usually star it. Then when I'm later looking for a library or piece of software I usually search my Github stars first for a nice pre-filtered list of options.
I know I could also use a bookmark manager to keep track of interesting non-Github projects, but that's way too high-friction and so in practice I usually forget about them.
* There's also the social feed on the homepage where you can see which repositories your friends have starred/contributed to. I don't personally use this super often but frequently I star some repository and then notice a bunch of my friends starred it shortly after, presumably because they saw it in their feed.