Send a PM to George as he is the expert on cm usage. He wrote the TLBTLD.
The whole idea is to show a higher "reaction" to the control questions (if any), than to relevant questions. Relevant questions are pretty easy to ident. With the FBI, questions might be something like "Have you ever stolen anything with a value over $100?", or "have you ever intentionally divulged classified information to any unauthorized person"...etc.
But you should be prepared to explain reactions to controls. So, if you answered, "No", you haven't "stolen anything", they may say "well, I may have stolen a pen at school", or some other minor thing.
The most important thing to remember is you are WALKING INTO AN INTERROGATION! They are NOT your friend, they are NOT there to help you, though they will tell you they are. They will lie to you and claim the machine can actually detect "deception". It can't! They're whole goal is to see what dumb things they can get you to say or admit to. If you show persistent reaction on a given relevant question, they will ASSume you are lying. Their goal THEN, will be to get you to say anything at all with which they can distort and turn into a "disqualifying" admission. Read some of the "personal statements" linked on the home page of this website to see how they can twist, distort, and blow out of proportion insignificant info divulged by an innocent, but naive applicant.
It's easier for them to do this than you think. The will attempt to wear you out, trick you, try to be your buddy...etc. They are TRAINED INTERROGATORS! They will try to frustrate you, and get you to the point where you will say things you otherwise wouldn't just so you can "end this bullshit and get out of here".
Do a google search on "false confessions"., and "interrogation techniques". You might start out with this:
http://www.nasams.org/forensics/for_lib/Documents/1104868281.86/Conti%20article%... Then again, you might show little if any reaction to the relevant questions, and get out through it without too much difficulty (i dunno maybe not with the FBI), and pass. Don't be belligerent, angry or smart alecky with them though.
Again, talk to GM. Using CMs at the wrong time and in the wrong manner can indeed backfire on you.
TC