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If one were to augment one's physiological responses to each question asked, it would likely produce an "inconclusive" outcome at best. I suspect that the polygrapher, seeing strong physiological responses to irrelevant questions, might also suspect that countermeasures were being employed.
Thinking about the same thing on each question is not the way to pass a polygraph "test": the key is to produce stronger physiological responses to the relevant vs. the so-called "control" questions. To ensure that you do this, you must first be able to identify at least one of the "control" questions. You'll find this all explained in Chapters 3 & 4 of The Lie Behind the Lie Detector.
Study these chapters carefully; understanding how the "test" really works will help to alleviate your nervousness. For more on what to expect, see also the Department of Defense Polygraph Institute Interview and Interrogation Handbook (a big file: 5.2 megabyte scanned PDF file, but worth the wait):
I have a question about breathing and contracting the anal sphincter. I know it says to do this only on certain questions such as controlled questions, etc. But, would it be possible to just do this on every question before giving an answer, regardless of the type of question? Also a friend of mine that took a polygraph said that he just thought of the same thing on every question. Such as, he would think of horses, cars or whatever. Does this help? My polygraph for employment is coming up and although I have nothing to hide, I am extremely nervous.....