External USB and flash drives are easy to lose, and all someone has to do is plug them into their computer to access your files. With that in mind, if you ever transfer or store any sensitive documents on external drives, you should consider encrypting them, which requires you to enter a password before you can get at your files. You can buy drives that come encrypted or you can encrypt any drive yourself. Whatever route you go, it's best to use those with 256-bit AES encryption. Also, consider buying those carrying the government-standard "FIPS 140-2 Level 2" or higher certification.
Secure your social network accounts
If you aren't taking on social networks seriously, it's only a matter of time before you get taken by malicious links and social apps that try to steal your personal information or money, or spread spam. And that doesn't even include the privacy issues in play--you probably don't want your employer to see all your personal life. So consider securing your social network security and privacy settings. Take a close look at the security and privacy settings for the social networks you use; learn what each of the settings mean, and adjust them as you see fit.
Also, think about using a security app to help catch threats and keep up with the latest threats via sites like Facecrooks. Some current security suites, like Trend Micro's, include features that will check your Facebook privacy settings, and offer suggestions for improving your privacy.
Sign up for online backups
You probably know that you should create a backup of your computer's hard drive, just in case. But what happens if your backup disk goes bad? Using an online backup service is a good way to protect your most valuable documents, just in case double-disaster strikes and both your hard drive and backup go dead, or both are destroyed in a diaster. There are plenty of services out there, and some antivirus companies provide online backup services for their customers.