Software inspection is the most powerful static quality assurance method. However, the inspection process needs to be monitored continuously and refined when it is not producing expected results. We suggest using prescriptive metrics for following the effectiveness of the inspection process and process pattern approach for introducing improvement actions that steer the process into right direction. We have analyzed the inspection process data from two year time period in a large software development organization. The data is compared to organization-specific prescriptive metrics. The measurements show that limits set by metrics are exceeded in some cases and the process needs improvement. Prescriptive metrics set helps in identifying the weak points in the process. Patterns provide a lightweight and practicable approach for defining the targets of improvement. In the case organization, prescriptive metrics and patterns worked well in instantiating the inspection process improvement.