Here’s a recent discussion of the merits of various password managers.
Nowadays, any other solution, whether that’s patterns as @RTFirefly says just above, @Joey_P locked word documents , sticky notes, etc., just seems silly. And yes, I’ve used all those “solutions” myself.
Yes, there is the one-time effort of logging in to each and every site or app you currently use. But you can simplify that by simply creating your password manager entry the next time you use that site for it’s own sake. Pretty quickly you’ll have loaded the ones you use regularly. You may also be surprised how many you haven’t used in years that no longer work because that company is gone, or has replaced their e-commerce platform twice since you last logged on and didn’t migrate the users, etc.
Bottom line, having done it myself for about 300 logins a couple years ago: It sounds and feels like a bigger project than it is, the security gains are palpable, and the convenience gains are huge. Net, net, I’m very confident my conversion effort has paid off in less total work here ~2 years later