"Most people use passwords. Some people use passphrases. Bruce Schneier uses an epic passpoem, detailing the life and works of seven mythical Norse heroes."
I take a passage of reasonable length from a book that I've memorized, could be song lyrics or anything though. Then to create a password I take the first several words to make a password roughly the length I want, do a standard transformation on it that results in a string with numbers and special characters and use that as a password.
When I need to change my password, I just take the next phrase from the passage and apply the same transformation. This has the distinct ability of letting me go back in time and remember what password I would have used at a certain time which has come in handy for remembering the root password on an old server.