So, here they actually make users' instructions for pot. Here is a nice list of dos and don'ts from a local coffeeshop's packaging:
(Translated from Dutch and shortened a little - don't Dutch people know this shit already?)
1) Use cannabis for pleasure. A joint doesn't solve problems.
2) If you smoke every day, try not to smoke a couple days a week.
3) Cannabis affects concentration, therefore, don't use it at school, work or in traffic.
4) Some kinds of cannabis are stronger than others and have a higher level of THC. An experienced smoker knows precisely when he has had enough and can then stop. If you are smoking for the first time, you don't know how much you can handle. Inform yourself therefore, over what kind you should buy.
5) If you don't have a lot of experience with marijuana, it's a good idea to avoid drinking alcohol at the same time.
6) If you take medication and want to smoke, consult your doctor first. Do not use while pregnant.
7) Don't buy cannabis on the street. Find a bonafide coffeeshop.
8) When smoking cannabis, substances like tar and carbon monoxide are released that can be hazardous to your health.
9) When eating spacecake it is difficult to determine how much cannabis you are taking in. Before you know it, it can be too much. Start with a small piece. It can take from 45 to 90 minutes to take effect. Wait for the effect and don't eat another piece or you will take in too much.
10) Sometimes cannabis can have a bad effect. You can feel sick or nervous. Find a quiet place and eat or drink something sweet. Don't panic. After an hour, the worst is over.
11) Consider that if you mix cannabis with tobacco that you smoke tobacco too. Nicotine is addictive.
12) Don't take cannabis with you when you leave the country.
There you have it folks: the twelve step program to Amsterdam.