Some therapists are more effective than others, that much is clear; why they are more effective is less clear. To answer this question, Louis Castonguay and Clara Hill compiled this comprehensive guide that brings together expert scholars and clinicians from a variety of theoretical backgrounds. They explore the empirical foundations of therapist effects as a broad concept and propose practical strategies to help mental health practitioners become more effective. Chapters also closely examine specific therapist characteristics, skills, and attitudes that are relevant to all clinical contexts, including therapeutic presence, technical interventions, cultural competence, reactions to negative emotions, and humor.