This refers to jigsaw listening or jigsaw reading. You have two cassettes or two texts on the same subject matter but the content should not be too similar.
One way of approaching the task is:
Present and briefly practise language necessary for the jigsaw. Remember that the students need to be able to recognise any new language on the cassette or in the text.
Have a general discussion about the topic area so the students are tuned into the subject.
The language and discussion stage could take place in a previous lesson, then just do a quick review in the jigsaw lesson to cut down on the amount of time spent.
You then split the class into two groups. Make sure the students with the same text are all sitting together. If you're doing a jigsaw listening, you'll need two rooms. Give them some questions to answer while they are listening / reading. They then compare their answers with others who have read the same text / listened to the same cassette. You should clear up any major discrepancies here.
You then pair the students up with somebody who listened to / read a different text. They tell each other what they heard / read.
To finish off the lesson you could have a quick review of the answers, clear up any outstanding points and where there is time, extend the discussion.
Jigsaw lessons are excellent for incorporating a variety of skills: the students get speaking practice, they also read or listen to a text and they practise listening to another member of the class. If you choose a topic of interest to your class, you can generate an interesting debate. Remember to leave plenty of time, as these activities can be time-consuming.