Some people can remember a lot very accurately. I don't have the best memory myself, but I reckon I could manage a phrase or two pretty easily.
What about remembering a chapter number of a book you have and using the first paragraph?
The passphrase would be much secure.
That's quite clever. You could have "Page 3 Paragraph 5 Sentence 4" written down on a piece of paper, and even if someone found the paper they wouldn't be able to crack your password unless they knew which book you were referring to...