come on guys, it's not that complicated
you can drink a gallon of water right before and you will basically piss water. this will work but you can get called on a retest for having "diluted urin" so definitely tell them that your on a workout program that requires a gallon a day if you do this.
the safest route is the wizinator. you can get the cheaper version without the dick for 60 bucks and it will work for 2 tests if you do it right. the dick version is about 160 but you can refill it so it's got it's perks. for corporate drug tests (for a corporate job) you only need the cheap one, for the state you'll have to go with the full kit and i'm not sure about blue collar.
i've done both ways and they both work. i have a friend that was on parole for a few years and did the gallon of water thing the whole time and it worked for him but i personally rather pay the money and not have to deal with any stress using the wizinator.
oh and if you use the wizinator, practice with the clamp first, it can make a loud noise unless you do it right, so get your technique on lock before you go piss. and if your company does randoms, then just keep one in your car.