Time needed: 10-15 min
Why? Every student is using once a while this method to recall knowledge. Let them do officially.
When? This method can be used after one topic is finished.
How? Let the students choose one theme out of the taught topic, or give everyone one question connected to the taught topic. Then tell them to create a cheat sheet with key words about that topic. The letter cannot be bigger than the students hand. After everyone is finish, let them stand up and speak about the question without using the sheet.
Any risks? Students will do that, with your help or without, it is a good method to compress the taught topic.