In Peer Instruction, all the students in the lecture "vote" on the answer to a question, before and after discussing it with their neighbours. This can be done in several different ways:
Show of hands
The simplest system is just to use show of hands. After students have read the question and thought about it, the lecturer says `Hands up everyone who thinks the answer is A', then 'Hands up everyone who thinks the answer is B', and so on. The main disadvantage of this system is that it is not anonymous; students can easily look around to see how others are voting and choose their answer accordingly, rather than thinking about it for themselves. Nonetheless, this system can still be quite effective.
Each student is provided with a set of cardboard flash cards, labelled 'A','B', 'C' etc. Students vote by simultaneously holding up the card corresponding to their answer. The lecturer can then make a visual tally of the distribution of answers and report it back to the class; "OK, so about half of you have voted 'A', the rest seem to be fairly evenly split between 'C' and 'D'".
This widely used method has the advantage of being low-cost and simple to introduce. Voting is fairly anonymous because students cannot easily see how other students are voting; all students raise their cards at the same time and the cards are single-sided. This is the method we have used at Monash and we have found it to work very effectively. You can find a print-ready PDF of the flash cards we have used.
Electronic response systems
Each student can be provided with an electronic response system or 'clicker'. This is a small keypad which sends a signal to the lecturers' computer. The computer then tallies the votes and the results can be instantly displayed in the form of bar chart. Most systems also allow the lecturer to keep track of individual students' responses to questions. See the links page and the references section for further information.
The main advantage of using clickers are that voting is as anonymous as possible. Students cannot see other students' answers until the results for the whole class are displayed. This encourages participation and requires students to think for themselves about their answer.
Another advantage is that the lecturer can keep accurate records of how students answered each question. This is very useful for identifying questions that are either too easy or too difficult. If data is collected on individual students' responses to questions, this information can be used to identify students who are struggling and to keep records of attendance.
The main disadvantage of using an electronic response system is the initial cost and the technical support and training required to use it.