The research presented is motivated by the demand for process improvement for companies active within software development. High demands on software quality are a reality. At the same time, short development time and low effort consumption are required. This stresses the necessity for process improvement. Empirical research methods and close cooperation with the industry partner addressed the research challenge. The research presented in this thesis shows how the analysis of faults through fault classification can be used to determine suitable and required process improvements. Two alternatives are investigated. First, a lightweight approach, and second a fault classification approach targeting all faults. The suitability of the fault classification is stressed as well as the importance of assigning the correct fault class. The latter is determined by classifier agreement calculations. Additionally, the research proposes that the appropriate occasion for a correct fault classification is alleged to be when the fault is corrected. The research also introduces an approach to tailor the verification and validation process. The tailoring process suggested considers the functionality characteristics and the software entity complexity in terms of couplings. This is used to select the appropriate and efficient process for verification and validation.