There are a wide range of very different therapeutic approaches and a wide range of patients seeking our help. How do we decide which therapeutic approach to use with a given patient?
It would be great if there was a valid way to match patients to therapeutic approaches, however, the research on this issue which I've seen has not produced impressive results. The honest answer is that, in general, we do not have good ways to choose the best therapeutic approach for a given patient.
I believe that this is partly because for each patient there usually are a variety of different therapeutic approaches which can be helpful. I would argue that another reason for this is that the effectiveness of treatment is influenced by many factors other than the therapeutic approach being used (such as the therapist's skill, the fit between the therapist and the client, events in the client's life, etc).
A therapist needs to approach the question of selecting a therapeutic approach by asking What does the client want/need to accomplish? and What therapeutic approaches have a good chance of accomplishing this?.