In order to help a drug addict recover from his problem you need to first find out why he started doing drugs in the first place. It can be a little difficult to find out what started the drug addiction but if you focus and pay attention to the drug addicts life you can easily figure out what was causing the addiction.
There are many different reasons that will make people want to take drugs. The following are just some of the most popular reasons why people become addicted to drugs: peer pressure, depression, and a past history with other substances.
If a drug addict is addicted to drugs because all of his friends are doing drugs all you have to do in order to help him recover would be to first tell him that he has a problem and help him accept the fact that if he continues to hang out with friends who do drugs his life will get much worse. You need to separate the addict from his friends that consume drugs until he is cured. Of course you cannot separate the addict on your own; you must make it clear to him that it is for his own good that he stays away from people who do drugs.