I think the standard would be to use a password manager such as KeePass, with a long random passphrase such as five to six words chosen truly randomly from a la

I think the standard would be to use a password manager such as KeePass, with a long random passphrase such as five to six words chosen truly randomly from a large dictionary. A folder or notebook in your house is not terrible, actually, since it lets you avoid reusing passwords (though it won't generate strong passwords for you like a password manager will). Harder to back up. You might want to keep it in a fireproof safe.