Voters may like to look at the previous writeup before voting on mine.
If you don't have access to a thumbtack (What with you being in prison and all), you can use pretty much any other non-visible technique to create false highs when asked baseline questions.
Two techniques that can be put to quite effective use are biting down on your own tongue and clenching your buttocks as hard as you can.
The on-paper results of the lie detector test aren't the only thing you need to control, however. The FBI know that you can trick the lie detector, and thus don't rely solely on its outputted results. It is also intended as a psychological tool; They let you stew for a while locked in a plain room whilst they go and get the machine, then they hook you in, sticking electrodes all over your body to measure your responses.
With people who lack our knowledge, this is understandably stressful; they are hooked up to a machine that can see into their thoughts, a machine that can detect their lies easily. 'YOU CANNOT TRICK THE MACHINE, SON' it says, followed up with 'YOU COULD GET TWENTY YEARS FOR THIS, UNLESS YOU CO-OPERATE.'
It is, in other words, a tool for threatening suspects with discovery, in the hope they will crack and make a confession. Resisting the police trying to 'sweat' a confession out of you is half of beating the lie detector.