Actually best to not choose a pass'
word' at all. Best bet is to go for a pass'
phrase', or something made up from a passphrase.
You could (purely for example) take the first line of a song:
Code:
Shot through the heart and you're to blame, you gave love a bad name.
You've got upper case, lower case, and punctuation. Add to that the length of the thing and it's going to be near impossible to brute force, yet it's still simple enough that you can remember.
Failing that, you could develop it by logical and repeatable substitution, like this:
Code:
Shot through the heart and you're to blame, you gave love a bad name.
Stthaytbyglabn (remove punctuation, use first letters only)
$tt4&yt8y91@bn (now substitute letters for symbols/numbers)
Obviously your mileage with any of these techniques/suggestions will vary, and the effort you put into this sort of thing should always be balanced against the risk to your systems and the importance that you place upon protecting the data that they process/store.