I used to work in this area so I know alot about drug testing. Pot can clear in a week for occasional users, and up to 2 months for daily users. Usually one month is enough though. Drink lots of water in the week before the test and an hour or so before the test, it dilutes your urine so the concentration will be less. If the result shows too dilute a sample (specific gravity was too low), they may make you do the test again but this will buy you some extra time to clean the system. Like Lilith said the hard drugs clear out much faster. I tested people who told me they had smoked one week earlier but were not regular users and they tested negative, so it can clear out relatively quick. There are some products you can buy that claim to clean the system. Some labs look for these substances in the sample too, and they will make you redo the test if it is detected. I know some people who claim the "clean pee" stuff worked for them because they tested negative (but they may have tested negative anyway) and I know others who took the product and tested positive. Other than these things there is no way to cheat. I once had someone hand me a bottle of cold pee after cominmg out of the bathroom, lol. Obviously it was someone elses and they lost their driving job. Good Luck