How to make a strong and secure password
The key to making a strong and secure password is using all types of characters; symbols and different cases should be used many times to make your password near unbreakable. The easiest thing to do is to think of a sentence describing yourself or something that you care about; for example, the sentence could be: "My Favorite Game Is Halo 3". Now, just take the beginning characters of the sentence: MFGIH3; to make it even more secure, replace the 'I' with a '1', and add two asterisks at the beginning and end, having it look like this: **MFG1H3**. Then, make alternate the letters from uppercase to lower case. Your finished password would be **MfG1h3**, and you can easily remember it from your sentence that you made.
Also, it is not recommended that you use common passwords, like 'QWERTY' or 'QAZWSX' or '12345', or 'let-me-in', or your name or birth date; because they are too obvious and easy for a hacker to crack.
How to store your password securely and safely
It is not recommended that you write your passwords down on a piece of paper or leave them all in one place, since they can easily be stolen. Some other options include encrypting your passwords using a password management software or some other tool.
Password Strength Meters
MalwareTeks: http://www.malwareteks.com/tools/pwd_meter/ (loosely based off passwordmeter.com)
Password Meter: http://www.passwordmeter.com/