A useful way to determine students' intuitions on a given topic is to present them with a paradox or a puzzle involving the concept at issue, and to have them figure out a solution. By forcing the students to work it out without some authority's solution, you increase the likelihood that they will be able to critically assess theories when they are presented later. In scientific fields you can present experimental data which seems to contradict parts of the theory just presented or use examples which seem to have features which support two opposing theories.