Alter the Results of Control Questions -
The best way to beat a polygraph is to throw off the control questions. These are the questions you will be asked to get a baseline reading of your breathing, blood pressure, heart, and perspiration rates. Your other responses will be judged against these results. So when you are asked an obvious question, such as, "Are the lights in the room on?" alter your breathing. You should breath faster, slower, shallower, or deeper. You can even hold your breath. You need to do this for approximately 10 seconds after the question, and then return to your normal breathing routine.
Control Your Breathing -
After the control questions, breathe normally for the rest of the questions. Be very conscious of the length of your inhale and exhale. If you have a few days before the lie detector test, practice breathing by counting your inhales and exhales. This will ensure they remain constant over the length of the test.
Bite Your Tongue -
Bite your tongue hard enough to cause pain, but not bleeding. The will alter your stress responses that the polygraph is measuring and make it harder for the investigator to compare responses accurately. You can only use this method for questions that require a yes or no answer as biting your tongue for questions that require you to speak more than a word or two will tip off investigators you are trying to alter the results.
Tack in Your Shoe -
Another way to cause yourself pain and alter your body's stress responses is by putting a tack, nail or piece of broken glass inside your shoe next to your big toe. When you have to answer a questions that needs you to give more than a word one answer, press down on the sharp end of the tack.
Induce Panic -
Alter your blood pressure by thinking of something that makes you mad, frightened or frustrated. This will confuse the lie detector machine and skew the results.
Keep Your Answers Short -
When at all possible, keep your answers to a simply yes or no response. Don't give the investigators anymore information than is necessary to work with.
Think Complex Thoughts -
When responding to a question, try to multiply large numbers or say the alphabet backwards. This forces your mind to think of something else other than the stressful situation you are in and changes your body's physiological responses to questions.
Contract Muscles -
Try to contract your anal sphincter when you are asked a question. This method is also very effective, but modern use of pressure-pads you sit on can detect this. You can also contract your calf muscle or the bicep of the arm that is not connected to the blood pressure monitor.
Drink Some Alcohol -
Now don't go to your test wasted, but a shot of vodka (that can't be detected on your breath) will calm you down and put you in a more relaxed frame of mind.
Speak in Even Tones -
Don't stutter, speed up your responses or speak in a higher tone than normal. This may take some practices beforehand. Have friends ask you questions and answer with a deliberate lie while trying to maintain a normal and even keeled voice.