I am in a similar situation as I am about to get tested on tuesday. Awhile back I went to www.passyourdrugtest.com and bought some of their products to help in clearing out my system because I knew I wouldnt have the 30-45 days it would take my body to clear out all the THC. I know you don't have time to do that for your test tomorrow, but for future reference it may help. The other advice is good in terms of drinking a lot of water, but you should also do this...

Drink cranberry juice. Don't ask me how it works, but it does help in cleaning your system.

Take a multivitamin 2-3 times per day. This also helps with cleaning out your system as well as keeping your urine yellow color so that they do not suspect you of diluting your urine.

The day of your test, make sure the sample is not the first of the day it should be at least the 3rd or 4th. Take the sample midstream as well.

www.passyourdrugtest.com also has some really useful info... check it out and good luck!!