16. You can cheat your drug test
Nope. You can't. If for some reason you bought into some shifty drug test-beating panacea -- like a detox kit or drinking a virgin squid ink cocktail from a back alley in Chinatown -- and it worked, well, congrats! You just witnessed a coincidence. The only way to "fool" modern drug tests is to either bring in someone else's clean urine (make sure it's heated, they test for temperature too), or use a Whizzinator (with fake, synthetic urine). Or you could always, you know, quit smoking.
17. Weed stays in your system for 30 days
Without delving too deep into things like half-lives and THC levels, it basically breaks down like this: A one-time user should be clear in a matter of days. A weekly smoker, a couple weeks, tops. For a daily smoker, it could be up to a month or more, depending on the level of fat on his/her body, as well as individual factors like metabolism. THC is stored in fat, so exercising can actually help, though just sweating can't. So skip the sauna, and focus on burning fat.