Brain cells should be used to remember important things. Most important things are conveyed by i.e. poems. Although nobody learns literature citings by heart in the era of wikipedia, a straightforward way to have a strong password is to pick e.g. the first letters of each line of a poem (aka passphrase you should already know), as described in the man:
When choosing a new password, make sure it's unrelated to any previous password. Use long passwords (say 8 characters long). You might use a word pair with punctuation inserted, a passphrase (an understandable sequence of words), or the first letter of each word in a passphrase.
...then you upgrade to snowy, and later realize that a given lib is not compatible with your favourite password manager and shut yourself out until you manage to restore your access. For generating hard passwords, you might as well go for ssh keys and manage those. But tastes and customs differ...
When choosing a new password, make sure it's unrelated to any previous password. Use long passwords (say 8 characters long). You might use a word pair with punctuation inserted, a passphrase (an understandable sequence of words), or the first letter of each word in a passphrase.
http://linux.die.net/man/1/passwd ...RTFM has also been subject of debate for ages...