People make up passwords they can't remember, then they end up using 'password' as their password. As discussed in this brief article you need to think about passwords that are both secure and memorable:

Vu, who is a assistant professor in the Psychology Department at California State University, Long Beach, goes on to say that the average password is easy to crack, but access to biographical data makes guessing that much easier with favorites being birthdays and children’s names. "My colleagues and I use an easily obtained cracking device called LC4 to crack passwords," she said. "It sources a dictionary to try words and combinations of words. It often cracks a password without knowing anything about the user. My research says that 60 percent of passwords can be cracked within a few hours, and some in less time than that."

Proactive password protection demands a requirement of upper or lowercase letters, numbers, special characters, and the like. Users generate a private password from these elements. The idea is that using these mechanisms makes cracking a password that much harder but her research has found a big trade-off between memorability and security. "The easier to remember a password is, the easier it is to crack," she said. "The ones that are harder to crack are the ones that are hard to recall and there’s the problem."

When you think about all the important things (your money, your personal information, your financial and legal records, etc) that you access online via passwords, you begin to understand (most people reading here probably already do understand, but hey, you can use this article to harangue your colleagues and loved ones) why it's really, really important to have secure passwords. Passphrases rather than passwords are more difficult to crack. Taking things you can remember and twisting them in ways that they are more difficult to crack (include symbols and numbers for example) but still something you can remember provide one way to keep more secure passwords.