There is little that you can do to prevent an NSA (or CIA) polygrapher from mischaracterizing your remarks if he/she is so inclined. Since applicants, employees, and contractors of these agencies cannot obtain their polygraph records via the Privacy Act, in many (probably most) cases, they have no way of learning whether the polygrapher has inflated -- or even fabricated -- an admission. Not surprisingly, it is not known how prevalent such polygrapher misconduct is. The NSA reportedly records polygraph examinations, which may serve as a deterrent to such behavior.

If asked about exposure to second hand marijuana smoke, you might mention that you've smelled it before (as virtually everyone has) rather than having "inhaled" it.

I potentially have a lifestyle poly coming up.  I have never used drugs before.  However, in college I was exposed to second hand marijuana smoke many times.  I saw in NSA Reject's personal statement about his polygraph experience that his polygrapher asked him if he had ever inhaled second hand marijuana smoke.  When he said that he had at concerts several times, the polygrapher twisted that into an admission that he had smoked marijuana ten times.  So how should you handle it if asked if you have ever been exposed to second hand marijuana smoke?  It seems that if you claim that you never have, it will look like you're lying, but if you claim that you have, they can twist it into an admission.  I also remember from NSA Reject's personal statement that during his third interview he was questioned about every single opportunity he had to do drugs.  I cannot possibly remember this, and considering that they ask you the same questions multiple times, I would almost certainly get confused on the dates and details of every single opportunity I've had to use drugs.  So how do you handle such a question?