And how to beet them.
A polygraph test can not tell if you are lying. It shows how much you are sweating and how fast your heart is beating and, passably, several other factors.
This is compared against a base line of responses from a set of 'neutral' questions given at the start of the test.
So to beet the polygraph test all you have to do is make sure that your responses to the neutral questions match those of the questions the operator wants you to answer.
The easiest way of doing this is to put something small and sharp in your shoe and press down on it when answering the 'neutral' questions. Then complain about being nervous and ask if this will affect the test.