It's a bunch of letters and numbers. I do have it written on a slip of paper though, so I (hopefully) won't have an issue if I forget. I also have to log in/out every day, so that'll really drill it into my mind. After the first few weeks I don't even think about typing in passwords. It's just muscle memory.
...Hopefully that paper doesn't end up misplaced.
I tend to use games that I enjoy as inspiration for my laptop login passwords, making them quite easy to remember. As for online login passwords (like, say, here), I let Dashlane auto-generate alphanumeric strings, and let it store them.