Against the background of the increasing trend towards tailoring psychotherapeutic procedures to the needs of the individual patient, this study aims at the formulation of empirically validated heuristics to guide the therapist's session-to-session decisions. A new research strategy, ‘selection from natural variation’, was employed, and the selected samples of therapy sessions from four different phases of therapy were subsequently examined with regard to their process and outcome characteristics. Process characteristics were assessed by ‘therapy spectrum analysis’ and outcome characteristics by the ‘Bernese Post Session Report—Patient Form’. Meaningful co-occurrences of process and outcome variables were identified using ‘feature pattern analysis’, which is a statistical procedure especially suited to the task of identifying underlying regularities in heterogeneous samples. The extracted rules specify the mixture of resource- and problem-focused interventions suited to the different phases of therapy and can be translated into guidelines for the continual adaptation of treatment procedures. Copyright © 2005 John Wiley & Sons, Ltd.