Improving performance of production systems is a critical but often unstructured activity. To help managers convert ad hoc or trial & error improvement efforts into efficient and systematic reviews, we develop a diagnostic tree which decomposes a performance improvement objective into successively more concrete sub-objectives and finally into potential improvement strategies. Based on principles from the Operations Management literature, this tree is structured to enable a non-specialist to better understand the links between corrective actions and performance. It also provides an important foundation for a principles-based knowledge management system that couples the decision tree with a search engine for locating relevant documents within an intranet.