Tips from the American Academy of Pediatrics:
Keep up with technology. Become familiar with popular social networking websites.
Enable privacy features. Install parental controls on your child's computer.
Check up on your children. Parents should let children know they are aware of their online presence and will be keeping an eye on them. Periodically check a child's chat logs, messages, emails, and social networking profiles for inappropriate content, friends, messages.
Limit time spent online. Limit your child's Internet and cell phone access. Children and adolescents who have unrestricted use of the Internet and cell phones are at increased risk for being exposed to sexually explicit material.