Since its inception, increasing clients’ capabilities in experiencing and managing emotions, interpersonal relationships, and crises has been central to both the theory and practice of Dialectical Behavior Therapy (DBT; Linehan, 1993a, Linehan, 1993b, Linehan, 2015a, Linehan, 2015b). Enabling clients to learn new skills, and to effectively implement them to change behavior, requires both capability and motivation on the part of skills trainers and individual therapists alike. The most effective DBT practitioners precisely assess at each stage of skills acquisition, strengthening, and generalization to determine how well their clients perform new skills. They assess what barriers are preventing effective skills use, in order to implement a focused endeavour to overcome any obstacles. This paper reviews principles of skills assessment within each treatment modality and provides therapists with checklists for identifying problems, and case vignettes illustrating helpful therapeutic strategies.