We all know password is important. If it is a master password for your password manager, it is super important. But how to choose a super strong one?
Security researchers and Snowden recommend using passphrases instead of password. Passphrases are usually very long though they are less complex. WHY SECURE PASSWORDS NEED LENGTH OVER COMPLEXITY
Permanent Record, Snowden's book, is worth reading.
I recommend using a sentense describing what/when/where you did/will do.