I'm sure I'm largely preaching to the converted here but the wonderful Computerphile have released a video on password selection on You Tube. Worth a look.
https://www.youtube.com/watch?v=3NjQ9b3pgIg
To reinforce the point here's the guy cracking some of a password file.
https://www.youtube.com/watch?v=7U-RbOKanYs
I highly recommend this channel and its sister channel Numberphile. Fascinating.