“Be sure to use a strong password” - The Traditional Password Advice.

A strong password is — which is still good :

• Has 8 Characters, Minimum: You need to choose a password that’s long enough. There’s no minimum password length everyone agrees on, but you should generally go for passwords that are a minimum of 8 to 12 characters in length. A longer password would be even better.
• Includes Numbers, Symbols, Capital Letters, and Lower-Case Letters: Use a mix of different types of characters to make the password harder to crack.
• Isn’t a Dictionary Word or Combination of Dictionary Words: Stay away from obvious dictionary words and combinations of dictionary words. For example, “Good” is a terrible password. “sounds good” is also very bad.
• Doesn’t Rely on Obvious Substitutions: Don’t use common substitutions, either — for example, “G00d” isn’t strong just because you’ve replaced an o with a 0. That’s just obvious.