The strong passwords we generate are long
(≥ 16 characters), contain lower-case and upper-case
letters, numbers, and symbols in a random
arrangement. A computer will need more than a trillion years to crack
one of our 16-character passwords.
Examples of strong human-memorizable master passwords
are long phrases that don't make sense and don't
show up in literature. "The Grass explodes like never
before And we sing a Song." (you could use it without
spaces if they are not allowed).
Never use single dictionary words, names, etc., even if you do some
common replacements like "a → 8" etc.