day 1, stop smoking and eat nothing but protien and drink lots of water and coffee with no sugar. The protien encourages the body to start burning fat. As this fat is burned it releases its stored oils. coffee is a powerful diuretic, drinking lots of it with lots of water starts flushing the body.
Sounds like a good method, but this part might backfire on you. If you trigger the body to start metabolizing fat, it could increase the level of THC metabolites in your system, which might make it more likely to be positive, especially if you are a long-term smoker.