It's tough when a friend needs help and you're kind of stumped as to what to do next. Often, finding out more about what your friend is experiencing is a good start. So is asking them. If you're unsure what to do, you can always say, "I want to help you but I don't know what to do. What would make you feel better?" Be prepared for what they might say. It may be much different than you originally thought.
Once I asked a friend this question after the death of a family member. I was certain she was going to want to talk about the person that died, but instead she said if she could just have someone drive her to the funeral parlor that would take a load off her mind. In all the fussing we were all doing, no one was asking her what was on her mind at that moment. She wanted to go to the funeral home to make sure everything was set. This was what was on her mind at first.
People need support differently for various types of issues, from addition to health issues to even divorce. Here are a collection of resources to help you help a friend.