I prepared this for an upper-int to advanced adult class. I adapted it from an article from the Guardian. It really got the students talking and debating. They were really interested. The best way I found was to start the class with a general discussion about science and the future. I prepared various general questions and found that the students introduced the topic of cloning by themselves. We then talked about what we already knew. I included a short text about "how it works" as much for myself as for the students as it's quite a complicated process!