Well this is a bit late, but here is what I did (maybe it will help others).
Pick 1 topic for an example. (Internet)
Introduce it, talk about it a little... (Do you use the internet? How often? What do you do? Here's a statistic...Teens spend 9 hours/day online! Can this be a problem? Why?)
Then, introduce Pros vs Cons.
Break students into groups and make them brainstorm Pros and Cons about the Internet.
Go over it.
Introduce how to say an opinion (In my opinion...In my experience...I think that...etc)
Go over how to debate.
Break the class into groups of 6.
Give each group 2 worksheets, and 1 stack of topic cards.
1. Pick a topic.
2. Rock, Paper, Scissors to decide which side will be pros and cons. (Winner: pros)
3. With your side, write down your opinions. (If 3 people are on 1 side, then they need 3 opinions. 1 for each person).
4. Debate.
5. Pick another topic, repeat.
Attached are the Powerpoints I used.
They worked like a champ :)