I'll echo others and say "with my brain" ... with some help.

I keep things store in a locally accessible device - not the cloud or a password service - and use all sorts of reminders to help me.

I just don't trust the various storage systems or password services to be secure. I'd rather blame myself for a blown password than having to change ALL of them b/c one of these services gets hacked. I'll admit they have some pretty serious sounding security in place. But, sadly, I've seen that same description applied to many other services I'm in that did get hacked.