How to choose a strong and secure password? The obvious answer is to choose a very long password and the next answer in the list is to include as much special characters as possible. But doing so would make it more difficult to remember and would even force us to jot it in postits.
But the ideal solution would be to choose a password which takes longer time to crack. Hackers can find someway to crack our password, all we have to make them try stronger and harder. Passwords are usually cracked using a method called as Bruteforce attack where a malicious tool tries to match all the type of password combination available against the target system. More complex the password is, more are the combinations to be tried and less probable it becomes for the tool to guess our password right.
This website, HowSecureIsMyPassword, gives us an idea on how long it takes to crack a password with a normal desktop PC. We can try various combinations, longer password/different character sets and analyze the results.
So as mentioned earlier we should choose a password which takes at least more than ‘a year’ to crack. This arbitrary value – ‘a year’ is based on the assumption that we would change our passwords once in every year so by the time the cracker obtains our password, we would have changed it 
