Belladonna as a drug is highly dangerous and unpredictable, you do know that right?
However if your determined to try it anyway i'll tell you what i know:
first things first the chemicals in atropa belladonna that you have to be worried about are the tropanes and the traces of these chemicals varied in batchs or even individual plants so different plants could be stronger than ones you've taken before.
the root which is harvested in autumn is the strongest part of the plant and best left well alone(death could occur through complications at as little as 1 gram). The leaves have the second lowest amount of tropanes and should be taken at the amount of one leave boiled into a tea for about half an hour will be more than enough for one person BUT drink it slowly and stop half way down the cup for about half an hour to allow your body to accustomise to the chemicals within the plant.
Another warning i'm afraid:if your boiling a dose for more than one person don't put everyones dose in one pot and boil together and split as the dose's be uneven and you'll be making a trip to the hospital....or the morgue!.
The flower i think is the best part of the plant as it's got the most
regulated amount of tropanes one/two flowers.
Make sure you have a babysitter (someone not on strong drugs who can look after you) who can stop you from wandering outside and away or hurting yourself or take you to the hospital).
tell your babysitter how much you have taken and keep a sample of the plant so the hospital can identify it if the worst happens.
Thats all just be careful.
for more info check out
www.erowid.com.