Before the TBL lesson start, the teacher will make some preparation materials available for you. These preparation material can be readings, videos, papers, etc.
Now, if you don't want to be bored during your TBL lesson, it is highly recommend that you go over the preparation materials thoroughly before the lesson.
This is quite important as the lesson - as well as your interaction with other teammates, will be based on these materials.
And you will be assess on your preparation as well.