If you don't trust your computer to produce random bits securely, use diceware to generate passwords, which involves physical dice and a printed word list. If you do trust your computer (or you think cameras can see your dice and word list), you can use dicelessware.
You'll need a dictionary file at this location:
$HOME/.dicelessware/active_list.txt
dw <wordcount>
Generate a pass phrase with wordcount words.
viwl [-f <file>]
Edit the default custom word list, or the specified file.
pin <charcount>
Generate a PIN with charcount digits.