Just always remember that a reaction to the questions means nothing really, particularly if you can explain it.  For example, I know someone who told me he got a big reaction to the question about drugs and another question about whether he ever commited any rape, molestation, or other sexually based offense.   

Well when he was sixteen he found his father dead in the living room from a heroin overdose and the subject of drugs always upsets him.  He sister was raped by a stranger and they never caught the person.  He was able to explain that to the examiner to justify his reaction on that series of questions.   

Hopefully, you can point to some concrete things if you react to specific questions.  But also bear in mind that one of the purposes of the polygraph is to try to coerce an admission or confession out of you, even if you didn't do anything.