If you're just an average user concerned about your privacy
- Use Tor when browsing. You don't have to use Tor all the time (it does slow things down considerably and some sites will also block Tor traffic). But if you are looking at or for something that you feel is sensitive, then either set up your browser to work with Tor or use the Tor browser.
- Use a password manager. It doesn't matter how many surveys and reports come out that tell people to use different passwords and complex passwords, a huge percentage of us maintain borderline idiotic approaches. The simple answer is: get a password manager. It will protect you.
- Use two-factor authentication. Many services such as Gmail, Twitter, Dropbox, Hotmail, and Facebook offer this now for no charge. So even if your password does get exposed, you still have a backup such as a text message to your phone to secure your information.
- Use apps that protect your information. Snowden suggests the smartphone app Signal, which encrypts both your phone calls and texts. It's free and easy to use. Although of course, following a high-profile argument with the FBI, it would appear that Apple's messaging service is also pretty secure (although Snowden would probably have doubts).
- Use the HTTPS Everywhere browser plug-in. This comes from the Electronic Frontier Foundation (EFF) and will try to force all browser communication to be encrypted.
- Encrypt your hard drive. This is comparatively easy these days but you have to be careful to do two things: one, have a longish phrase to make it worthwhile; and two, make damn sure you remember that phrase. There will be a slowdown in performance but nothing too bad if you have a modern machine.
- Be smart with your security questions. Stop using your mother's maiden name for everything. Likewise your first school. The key is to mix things up as much as possible so if someone does get into one of your accounts, they can't use the same information to get in everywhere else.