Summarize:

If you feel the need to cheat or manipulate the test, one thing that most people recommend is to cause yourself mental or physical stress when you are expected to give the answer to a control question. This will give you a higher baseline, so when you tell lies relevant to the case or situation, any spikes in your responses might be smaller than the spike you just created during the control. Think of a frightening or exciting thought when you recognize an obvious control question. You can also make your heart rate and perspiration increase by trying to solve a somewhat difficult math problem in your head. Try dividing 563 by 42, or some other similar problem. When asked a question relevant to the case or situation, put yourself in a calm state of mind when you answer. By staying as calm as possible, you can prevent many major spikes in your physiological responses. Essentially, a "lie" only counts if that lie generates a greater physiological response than that which you had while you were telling "white lies" with the control questions. As long as your physiological response to a question and answer produces a less noticeable reaction than any reaction you displayed while answering the control questions, it will probably not count against you. Maintain your breathing pattern and keep in mind that the polygraph is not infallible, and that you are in control of your own physiological response. Daydream about something soothing, like cuddling under a warm blanket with a cup of hot chocolate on a cool night, or taking a relaxing shower or bath. If the examiner catches you trying to cheat the test, you might be asked to schedule another test or the examiner may take countermeasures against further acts of manipulation. Moreover, attempts to manipulate the test might cause the examiner or reviewer to judge your results more harshly once you finish. For instance, do not stick a thumbtack in your shoe and attempt to press down on it to spike your vitals during control questions. Oftentimes, an examiner will have you remove your shoes during the test to avoid such tricks. In fact, while physical pain will cause your vitals to spike, it is usually easier to catch than psychological stress. Biting your tongue, clenching a muscle, or other similar tactics can be caught easily if you are working with a trained polygraph professional.
Stress yourself out when answering control questions. Calm down when answering relevant questions. Avoid tricks that are easy to catch.