Nail in the Coffen

[treetop]

A friend of mine is a detective for a local police agency.  he was giving me advice of the up coming polygraph.  He told me that the pre-test is where people faulter and the post test is where the nail the coffen shut.  He also said that the polygraph test itself is the least important of the tests.  He mentioned the only way to pass is to be 100% honest, be disconnected (sociopathic), or to just not care about the test (stress levels will be lower).
He said that countermeasures do not work and that good polygraphers can detect them.   I know he had not personally been trained to administer the polygraph so he may not know the "truth" about polygraphs.  Any thoughts?  I have my poly coming up in a month or so and I do have to "bend" the truth a bit.