lawrence,

Just a word of advice on the FBI polygraph - if you've used illegal drugs but are within the stated drug policy, I would highly recommend that you admit to your drug use and go on from there.

I recommend this for two reasons - first, although the polygraph's accuracy is arguable, I do honestly believe that if you are asked about drugs after having denied any use and subsequently have the instances in which you used drugs on your mind, you are only going to make the exam that more difficult for you to pass.  Even with countermeasures you are only making it harder on yourself if you are still reacting strongly to the relevant questions.

Further, an applicant that denies any drug usage period is going to be pressured to admit to drug use more than candidates who admit to limited drug usage.  Again, this will only augment your reactions to the relevant questions relating to drugs.  Not good.

In any event, if you are outside the stated drug policy or otherwise plan to lie on the relevant questions, I urge you to not take the polygraph and withdraw your application.  Realize that it is wrong to use countermeasures to pass a polygraph only to get a job that you are not qualified for.  If this isn't the case, good luck with the process.

I greatly appreciate your point George.  My situation is such, however, that I am going for a job with the FBI that I would be able to get otherwise.  It is a translation job from an obscure language that only the FBI would have interest in. 
Although I had considered working for the State department.  I currenty have no interest in working there, and therefore my failing on the exam won't have any tangible consequences.
Is the FBI polygraph more difficult then private polygraphs?  I have spoken to people that have lied and passed a polygraph.
I am denying that I ever used drugs illegaly and mainly hoping in imagining cognitively that this is the case.
I am not looking forward to it.  But I would like to give it a shot anyway.

Lawrence,

Unless your friend runs a business that is in one of the few sectors exempted by the Employee Polygraph Protection Act (such as an armored car company), it would be illegal for him to ask any prospective employee to submit to a polygraph examination as a condition of employement.

In any event, I think taking a "practice polygraph" would be largely a waste of money. You'll find the polygraph procedure used by the FBI and other federal law enforcement agencies explained in the Department of Defense Polygraph Institute's "Law Enforcement Pre-Employment Test" document:

http://antipolygraph.org/documents/dodpi-lepet.pdf

However, before you submit to an FBI polygraph examination, you should be aware that the failure rate is about 50%. It is clear that many truthful applicants are being falsely branded as liars. Failing an FBI polygraph can have especially serious adverse career consequences not only with the FBI (you'll be barred from FBI employment for life), but also with other agencies. In my opinion, the risks are simply not worth the potential rewards, and it would be prudent for you (or anyone else contemplating going to work for the FBI) to cancel the polygraph, withdraw your application, and seek work with a more responsible employer. See my article, "Just Say 'No' to FBI Polygraphs" for more on this.

my best advice would be to NOT go through with this until you have an LEO job that doesnt rely on the poly. that way if it doesnt go well at least you will already be in the line of work you wish to pursue.

I am about to go through a polygraph test for the FBI in the northeast.  Would anyone know if it would be useful to take a polygraph privaltely before going taking the real one.  If yes, does anyone know of a polygrapher that would be willing to do it.   

I thought of having a friend call and say that he is hiring someone, and would like to hire a polygraph and I would go through the test.  But then, if the pretence for the test is a lie, I'm not sure that it would be of much help.

Thanks