Abstinence and time. Different drugs last longer in your system than others. The best advice is to not use drugs.
What? If I understand you right you are asking advice on how to pass a drug test? Please find a physician who will care for you and respect you no matter what is in the drug test. If it is because of legal issues well that's a wake up call that perhaps you have to address your drug use. If its for work, well i'd hope you could find work that doesn't induce you to "cheat" yourself first and foremost.
Abusing drugs. Not one physician here wants to help you stay addicted, selfish, or dishonest. We believe that the disease of addiction is real but that there is a treatment. The obsession to use can be lifted and health and relationships restored. Please don't ask physicians how to scam the system to keep abusing mind altering substances.