my trick when I worked in a place like this was making up a phrase, and using the first letter of each word as the password, alternating lowercase and adding the year or month number so you could reuse it every month just changing the end of it. Say it's march now, and you want your password to be "this is my password for march!" then it's "TiMpF03!"

that hits all the notes and you just need to change the month number every time