Buy a cleanser. Thats pretty much all you can do. I can always drink as much water as possible, but it depends on how long ago you smoked weed (im assuming thats what you do). I smoked a week before i had a test and the night before i literally drank about 5 or 6 gallons of water in a little over an hour. It sucked, but i passed the test. You can also go to GNC and buy a bottle of Goldenseal pills and swallow 20 or 30 of them muthafuckers. But the best bet is to buy a cleanser. EASY.