Do not use personal information. You should never use personal information as a part of your password. It is very easy for someone to guess things like your last name, pet's name, child's birth date and other similar details.
Do not use real words. There are tools available to help attackers guess your password. With today's computing power, it doesn't take long to try every word in the dictionary and find your password.
Mix different character types. You can make a password much more secure by mixing different types of characters. Use some uppercase letters along with lowercase letters, numbers and even special characters such as '&' or '%'.
Use a passphrase. Rather than trying to remember a password created using various character types which is also not a word from the dictionary, you can use a passphrase. Think up a sentence or a line from a song or poem that you like and create a password using the first letter from each word.
If a thing's worth having, it's worth cheating for. -- W.C. Fields