The suggestions in Help:Login notifications#Have a strong password are not really up-to-date.
You should not really emphasize the need of special characters or so. It is easy to mathematically calculate (see Wikipedia; n=length of password; k=character set to choose from) that longer passwords are much more secure than a same-length password with more special characters.
This also aligns with new policies by the NIST. See https://nakedsecurity.sophos.com/2016/08/18/nists-new-password-rules-what-you-need-to-know/ e.g.