With the polygraph don't try looking it up on the internet or asking people about it. Get a good nights sleep, eat before you go in, don't drink any highly caffinated beverages and try to avoid any excess stress for a day or so prior.
Most importantly be honest with your anwers, believe me they have heard everything before!!!!!!!! Be honest in your interview as well, as some of those questions and the answers you provided will most likely be re-confirmed.
Everybody keeps that little locked box at the back of their head, full of items that they are too embarrassed or ashamed to share with others. Be prepared to spread that little box out on the table for the polygraphist to look through. It's about integrity and honesty, not that you smoked excessive amounts of BC finest chronic in Grade 10!!
Cheers
Noneck