According to Huffington Post, these are the top 25 most common passwords:
...So obviously, if you use any of those, you need to change them.
I use an app on my phone called 1Password to hold on my passwords, so I don't get in the dangerous habit of using the same password for all my log-ins.
And you might want to try this site that generates passwords for you that are pretty much unguessable. You can set the number of characters and whether you want symbols in your password or not.
Check out passwordgenerator.net here.