Don't smoke. If you have recently been placed on probation by the courts , Your probation officer is going to drop you . But if you can't kick just admit to your probation officer that you have a drug problem and you need help. I'm sure they'll let you slide on a dirty drop if its your 1st time, but if you already had failed one before they won't. If you think you can't stop go enroll in some drug counseling service before your drug test so it can look like you acknowledge that you have a problem and that you're trying to get help.
There are many myths, but they're all myths... it'll leave your body when it wants to, drinking water and trying detoxes makes no difference. Although the speed it leaves your system depends on your usage history, if you use it regularly it takes longer to exit your system, if I were to use it for the first time, it would definitely leave my system before even two weeks is up. I believe it should leave your system before a month is over... But why even bother taking that risk?