In a real polygraph exam a baseline is established and you review all the questions "before" the test is run so that there is no surprise when they are asked the second time. Even then the nature of the questions can elicit a measurable response.
The best advice I ever got from a polygraph examiner was to never voluntarily take one. Advice given while I was strapped to his machine. Never could be sure if he was being sincere or just manipulating me.