At the moment there aren't many ways you can have inventive passwords, usually a note just gives you it or says it's the date of birth of an individual. Another option could be that their password is contained within their phone number, for example "Remember, your password is the last 4 digits of your phone number" could be written. This would be a small way to add a little more variety on how you discover someone's password as it's not always easy to find.
#Taking passwords from phone numbers
rocky junco
rigid raven
Finding someone's phone number isn't that hard, but I agree that this would be a useful source of variety. It's not like it's substantially different in difficulty than finding their birth year