This can't be said enough: Use different passwords for every account you have, everywhere. Change those passwords at least once every 30 days. Use the most sophisticated passwords the system will allow, including special characters, alternating caps, and spaces where available.
I personally use keepass, with the browser plugins for automating credential input. I disable the browser storage of logins, and run all portable apps inside a sandbox, stored within a truecrypt container. Using a password manager allows you to use ridiculously complex passwords without having to remember them, and helps prevent you from falling into the habit of using the same credentials for multiple sites. It's also damn handy when it comes to rerolling passwords on a regular basis.