One of the best things you can do to prep for any type of testing is to abstain from drugs. This may seem like an obvious thing to do, but it's the only sure fire way to get a clean bill of health when you get your drugs tested.
The only problem is that it's not always easy to do, especially if you have a job, family or other obligations to take care of. Fortunately, there are several things you can do to help you stay sober until your drug test comes around, including stopping smoking and eating healthy.
First, drink lots of water (at least 8-12 oz a day) to flush out the system and keep it clean. Another thing to do is to work out and increase your cardiovascular activity. This will help flush out any toxins that you might have stored in your fat cells and help them move out the bloodstream.
Finally, make sure you are taking a multi-vitamin and mineral supplement to ensure your body gets everything it needs. This will ensure your body is functioning at its best so that your drug test is as accurate as possible.
In addition to these tips, the best way to pass a drug test is to avoid it altogether. This can be done by going out of town for the weekend, getting a job that doesn't require drug testing or just plain getting sober and clean.