In light of LinkedIn’s password disaster, I found this advice on choosing passwords to be very helpful:
Passwords are like housekeys for computer services. They are intended to be secrets that allow you to access resources, but deny access to others.
Here are some questions to ask yourself about passwords:
What are the passwords protecting?
If one password is breached how many other computer services become vulnerable?
Who else knows your passwords? How much do you trust them?
What services have your passwords? How much do you trust them?
How many passwords do you have to manage?
How do you manage your computer passwords?
via Computer Security Session 1: Passwords, Overview « KW FreeSkool.