If you are screwed get catherized... Or go to anabolicreview.com and read up on how to pass a drug test. It goes into an extensive discusion.
You could do the epitest. but they are testing for that now too. so you'd have to do blood work to make sure it's right.
If you decide to piss normal, make sure it's not your first piss of the day and do not give them the first or last part of your stream.. These are the dirtiest./
Also, take 5 aspirin before, thins blood
do not workout 2-3 days before.
Drink Cran/grape/and water.
Take B-complex vit, Vit C to give diluted piss color
etc. there are a shit load of things you can do...
Go to the site I gave and read up on it.
Hope this helps