Polygraph Countermeasures?

[JSP]

Hi,

I have read "Lie behind the Lie detector test" and have a few questions about countermeasurance.

Let me state, i have nothing to hide and lived a life of honesty. Yet like all, i have regretted certain things in my life (mistakes), but nothing that endangers others or is against the law (choices about life moves, such as picking a social science degree rather than mathematics path...). Yet there is a police exam coming up, if i pass everything that leads to the polygraph test, i am wondering, when should i employ the countermeasures when it comes to those questions?

Should i use them during the control question (which to show signs of bodily movement, increase heartrate and perspiration), then during the relevant question, i would be 'relax', so on the polygraph meter, it will show that i am stating the truth?

At that point i am confused on when to use countermeasures. I have referred to your youtube video, but that is still inconclusive, since it only describes of how to do it, yet when employed, the person taking the test failed at the end. Can someone explain it in a 'dumbed down' tone so that an average joe can fully understand?