I use some combination of the license plate numbers from the cars I've owned over the past 25 years. This works well because it is not an easily guessed password since there are no actual words in it.

I never use a license number of a car I currently own.

This has given me the ability to generate somewhat random passwords that I can easily remember and the numbers and letters mean nothing to the general public. Using this method I've created passwords up to 30 characters long.