Facebook is considering ways to invite children younger than 13 onto its social network, a controversial move that could bolster the company's bottom line but also spark concern among regulators over the safety of young Internet users.

We asked an expert on the subject for advice on how parents might prepare for supervising children on social media sites. Stephen Balkam is head of the Family Online Safety Institute, which helps companies share online safety practices.

Q Why is it a concern that kids younger than 13 are on Facebook if those kids have a parent monitoring their use?

A There are plenty of underage kids on Facebook without their parents' permission or knowledge. And if a 12-year-old says she is 21 to get onto Facebook, then her default is to an open, public profile, which is the worst of all worlds. And even for those who do have parents monitoring their use, it would be far better for the tweens to have a specially built part of Facebook in which to share and communicate.

Q How can a parent best introduce and monitor their child's use of Facebook and other social-media sites?

A First of all, make sure to have a conversation (or two!) with your child before they go onto a social-media site. Ideally, sit down and talk through a family safety contract, and set the ground rules and house rules for using Facebook and other sites.

Next, friend your child on Facebook, Twitter, Tumblr and other sites. And then, if and when issues arise, talk things over again. If your child steps over the boundaries, then enforce a sanction that is reasonable and related to what has happened.

Above all, keep up a regular line of communication with your child.

Q Anything else a parent should keep in mind?

A Be aware that if you buy your child a smartphone, he or she may well have access to Facebook and other social networking sites when they are at school or at a friend's house. Make sure you create rules for these situations and use parental controls on their phones, as well as the computer in your home.