As originally conceived, the multiple choices of a well-designed ConcepTest would capture enough misconceptions that only half the class would initially answer it correctly. This sets up an ideal situation for students to discuss the issues that are involved and the success of these debates is reflected in more correct answers in a second vote.
However, it is not easy to always hit this mark, and it is not necessary to. The occasional relatively easy ConcepTest that most students answer correctly right away establishes some confidence and common ground. Students don't learn much from these, but it gets them comfortable and warmed up.
At the other extreme, a ConcepTest can sometimes lead to bewilderment. In such a case, one can consider letting students confer even before the first vote. One can also give some guidance as to how to approach the question. When seeing blank faces, it is also useful to ask if there are any words in the question that students would like defined, because sometimes an unfamiliar word is the stumbling block.
Sometimes the initial answers to a ConcepTest are clustered in the classroom so that neighbors will not have disagreements to resolve. (This is especially so when the better students tend to sit together.) In starting the discussion, it is important to remind students that they may be wrong even if their neighbor initially agrees with them and that they should play devil's advocate among the answers.
Before letting go of a ConcepTest, it is important to consider why the right answer is right and why the wrong answers are wrong. Students may answer rightly for the wrong reasons and wrongly with reasoning that is almost right. After they have conferred, students are more eager to offer rationales for and against the various answers.
In extending the discussion of a ConcepTest, it is good to continue to include
as many students as possible, instead of just the ones who are more confident
and less shy. One way of doing this is to toss out short questions
that can be answered by all students with simple hand gestures. For example,
pointing left and right is useful for discussing the direction of reaction,
pointing up and down is useful for discussion the effects of changes in
conditions on various properties, pointing multiple fingers up or down can
be used to denote the positive and negative integers for oxidation numbers
and formal charges.