Don't give your email address to sites you don't trust.
Don't post your email address to public places online like message boards, comment boards, or even your personal website.
Keep your personal email private except from people that you really want to hear from. You can set up a second email account for registering for public Web sites.
Use an alternate email address when buying a product from a site for the first time or signing up for a new service. If you're a CenturyLink High-Speed Internet customer, why not use one of your 11 included email accounts for this.