I would start with introducing children to what personal information is and why it is important to keep it private. The following youtube clip explains it very clearly. NetSafe Episode 2: What is Personal Information?https://www.youtube.com/watch?v=jJdHKqs_pi8
A role play would be a great way to reinforce when it is appropriate to share the personal information and when it is not.
This will lead to the appropriate behaviour online and a discussion about internet protocols and safety. We could compare the manners we use in real life with the manners online. Here are a few links to show your class.
NetSafe Episode 4: Be Kind On Line! https://www.youtube.com/watch?v=0u6-2aCea-M
NetSafe Episode 3: Tell an Adult! https://www.youtube.com/watch?v=MxJX-porZtA