Make your password long

At least eight characters long, and the longer the better. Passwords shorter than 8 characters are easy to crack. Follow these password rules. Avoid common words and proper names. Use both uppercase and lowercase letters, numbers, and symbols. Trouble is, who can remember a password like Fm79$#Xk? Try a passphrase instead: When I was 7, my dog Dolly went to Heaven. This contains 42 easy-to-remember characters, follows all the rules, and is in plain English. (Not every system will accept passphrases; when in doubt, try it out.) The odds against anyone cracking it even with the help of a supercomputer are astronomical. Make your passphrase original. Don't use familiar or famous quotations. Don't use any real names especially your own, your family members, or your pets. Nonsensical passphrases are the hardest to crack.

Reference: www.sans.org