The advice I give above, 1 thru 5, are not countermeasures.
Countermeasures (biting tongue, puckering spincter, doing hard math problems in your head...etc.) are employed when answering "control" questions during the test, to increase your physical responses, so they are greater than responses when you answer "relevant" questions. So, first off, you need to know if the test even contains control questions. Not all polygraph formats do.
Do yourself a favor and read the "lie behind the lie detector"
http://antipolygraph.org/lie-behind-the-lie-detector.pdf before you take the test.
At this point, I would not concern myself with countermeasures and whether to employ them. You might be psyching yourself out, and end up employing them at the wrong time and in an incorrect manner.
Just
truthfully answer whatever drug use (etc) questions you are asked. Stick to whatever the truth is, nothing more, nothing less.
You may not even react to the questions and sail right through.
Just remember the machine can not detect true or lies, though they may try to tell you it does and that it is indicating that you are lying or bothered about something. This is not true and IF they do that, they are just "fishing". Let them do whatever they do, just don't admit to anything more than is true. IOW, if you know you are telling the truth, and are NOT "bothered" by a question do not let them talk you into thinking you are, so you end up saying something they can later distort and blow out of proportion to fail you!
Be polite, try to develop a good rapport with the examiner. Do not be confrontational, or debate the accuracy of the polygraph with them, or point out that you've been to this site and have researched and discovered that the polygraph is bogus! You might as well tell them their grandma is a whore! Polygraph operators hate this site and if you admit to coming here and agreeing with us that will be two strikes against you.
The idea is to be polite, cooperative and respectful, but secretly know what the polygraph is really all about (an interrogation disguised as a test), and sit there with a straight face when (and if) they tell you a bunch of lies about the test, or what the machine is divining about your most inner thoughts. It's funny when you think about it!
Good Luck