Here are some stimulating ways to start discussions with teenagers:
• Draw on students’ personal experiences.
• Ask students to reflect on their own culture and attitudes.
• Give students a concrete decision to make with their peers.
• Keep the conversation peer-centered—plenty of pair or small group collaboration.
• Keep to fairly short discussion activities (15 minutes) until you know what they like, and they feel relaxed enough with you to talk freely.
• Avoid asking discussion questions around the class; this puts them in the spotlight and causes potential embarrassment in front of friends. You also risk dominating the talk.
(Taken from: www.britishcouncil.org/language assistant-teaching-tips-teenagers-talking.htm.)