How To Help A Drug User

If I know a person who is misusing drugs but doesn't want to stop, my first instict would be to leave them alone since it's their choice, but my consience would force me to take action. Firstly, I would talk to the person about the side effects of the drug and how it can cause harm to the body. I would also show him ad's about not using the drug, in an attempt to not want to use the drug anymore. If it apears that the person really does not want to stop using the drug I would force him to talk to a counselour or even call the police, since the person cause greatly suffer if nothing is done.