Regardless of the specifics of each new tool, gadget, site, or app, it is important to communicate to children your expectations for their behavior online. Children (and even young adults) sometimes have a tendency to do things online that they would never do in "the real world." They need to be reminded that the online world is part of the "real world" and that what they do online has real repercussions on the lives of themselves and others.
Google has developed some family safety resources for parents and children to watch and discuss together. The link to their site is http://www.google.com/goodtoknow/familysafety/
Even if you don't know a lot about technology, these can be a way to open the conversation. Don't hesitate to ask your child about technologies that they know more about than you do- they might find it refreshing to be able to teach you something.