What are some common mistakes students make with cyclohexane chair flip?
Ignoring the utility of models in tests and exams.
Most examiners will likely allow the use of molecular model kits in exams. You can't take a dictionary into an English test, but you can (and should) take a periodic table and molecular models in a chemistry exam. You should make sure (i) that you do take them, (ii) know how to use them, and (iii) practise how to represent chair and boat conformers of cyclohexane (and its simple derivatives) on the printed page (i.e. you must learn how to represent the 3D model in 2 dimensions so it is clear to the examiner). Good luck.