the effing trick is easy man... its all about drinking water right before the test, theres alot of fat and shit in your piss that THC bonds with, and comes out with also. THC is not soluble in water at all, no bonding there, so all you have to do is drink shit loads of water like 2 hours or 1 all the way up to around the time you have to take the test. Your piss will be clear, because it's just straight water. It will be lacking protein, and thc. the lack of protein could possibly make you fail, so you take vitamins. Turns your piss yellow, but its still water, and gives it protein if im not mistaken. This has worked for me many times over at my probation, taught to me by my father lol. I've used it and passed at jobs too. Or if they aint looking at your junk when you take the just tape and elmers glue bottle full of clean piss right between your thigh and your nut sack (for warmth). I have also done this, many times..