For a long time I generated passwords using a custom algorithm that involved a standard base phrase and then some functions based around the name of the site or service, along with hashing, but everyone went and got totally different arbitrary password rules and that got untenable, so I finally gave in and switched to a password manage. <3 me some KeepassXC -- especially because it's not reliant upon any third party cloud provider (and thus not susceptible to a breach at such a provider). Nice plugins on all platforms I've needed it on too.