I am a heavy smoker at least a gram a day everyday for about 5 years, i am also a pretty heavy set guy (5'11, 250), i stopped smoking about 15 days before the test but was still failing the at home tests leading up to the real thing. my eating habits didn't really change until a few days before the test when i started eating lots of red meat and taking creatine supplements. i also drank alot of cranberry juice leading up to the test but i don't think it really did much.. Hope that helps and practice before hand also helps.:thumbsup::rastasmoke: