The first question that a family needs to ask is whether or not they should even perform an addiction intervention when trying to convince someone to take action and get help. There are some risks involved and many people do not even consider these before confronting someone. The risks include:
1) Further driving the addict into isolation.
2) Creating resentment in the addict for putting them on the spot or confronting them in a harsh manner.
3) Further pushing the addict away from the idea of treatment.
And so on. In other words, an intervention can sometimes create a backlash that obviously is not the intended outcome. However, if the addict is out of control and has become a danger to themselves or others, then the family may be willing to risk these things in order to try and produce change.
The caution here is not to perform a massive intervention if the circumstances do not warrant it. It should be an act of desperation because of these potential risks involved.
The family needs to do some planning if they are going to make an effective drug addiction intervention. The main thing that needs to happen is that the family and friends need to decide on the best possible outcome and define the goal of the intervention. If this is vague then it will not be effective or helpful in any way. For example, it might sound initially like a good idea to try and get the drug addict to agree to stop using drugs. This is a terrible goal for an intervention and it will not work. Why? Because it is not actionable or specific. The addict can easily agree to it and then walk away from the intervention and change nothing.
A better goal would be something that involves immediate action. A trip to rehab is the best actionable goal for most addicts in most any situation. Even more effective is if the family can set up the admission to treatment in advance, so that the addict has no excuses and no wiggle room at all. The ideal intervention involves taking the addict directly to rehab after confronting them, so that they are instantly put into a safe environment and can start working on massive change right away.
Anything less than this outcome is a compromise that will likely produce poor results. Aim for instant action with a trip to rehab. This is the ideal situation because it produces instant results. There is no guarantee that the person will stay clean forever, but at least they will be clean and sober for 28 days and start learning a new way to live.