A study that tested state-of-the-art password-guessing techniques found that requiring numbers and uppercase characters in passwords doesn’t do much to make them stronger. Making a password longer or including symbols was much more effective.
State of the art password guessing software has made the old recommendations of using upper and lower case or numbers obsolete. The best advice now is longer. One way to do this is to create a phrase that describes a vivid scene you can easily recall. For example imagine a Moose walking in the office with a toothache. The password could be “mooseneedsendo”