Which of these is the best response if someone you know is exhibiting many of the warning signs of substance abuse?

The best thing to do is to sit down and talk to them first. They'll feel much comfortable from it coming from you than others. Second thing is to try and refer them to help.You don't want to push them to the point where they don't want to try. But overall it is important for them to know that you are with them every step of the way.