If you don’t have much experience using VoIP, such as Skype or Google Voice, try calling another student or a coworker. Both services are free, have simple sign-up procedures, and include optional video.
Talk for a few minutes online. What differences do you notice between VoIP and talking on a cell phone? Discuss what you learned with the rest of the class, and then, as a group, generate a list of tips for people using VoIP.