Password cracking software uses one of three approaches: intelligent guessing, dictionary attacks, and automation that tries every possible combination of characters. Given enough time, the automated method can crack any password. However, even when password cracking tools continue to improve, it still can take months to crack a strong password. Here is one of the best tip on creating strong secure passwords:
Instead of using the same password for everything you access, choose a root password, then take the name of the service or application you’re accessing, replace a few letters with numbers (or jumble it up), and append it to the end of your root password.
OfZenAndComputing.com has some more strong password tips:
1. Do not use names, nor words found in the dictionary.
2. Your password’s length should be at least 8 characters long.
3. Select an alphanumeric password, meaning that it contains both letters and numbers. Try appending a random number to the end of the password, or replacing one or two letters with numbers.
Source: Create a strong, secure password | Passwords: The weakest link