In your mark book, number the pupils in which ever way you wish - I do it alphabetically. Ask a question, pick a ball out of the bag and direct the question to the pupil with a number against his or her name.
Pupils can see that the process is completely random and quickly get to know their number. An element of risk is introduced into the classroom, and questions are not directed to those who know the answer. All pupils have a chance at being asked, which helps them concentrate more on the task or issue.
Use the same method to check on homework outcomes at the beginning of a lesson by using the balls to choose four or five pupils to present a "show and tell"
Tony Fuller teaches history at Wadham School in Crewkerne, Somerset.