Increasing competition and fast innovation take up new challenges for engineer-to-order (ETO) companies to address special requests from customers without losing efficiency. The optimization of the trade-off between customization and operational efficiency is a core competence for ETO manufacturers. Most advanced companies are reacting by introducing an ETO Enabling Process, which is the process of transforming special requests alongside the ETO value chain into know-how to be subsequently reused with a gain in productivity. This paper, therefore, presents relevant best practices implemented within a research project with three ETO companies while adapting the ETO Enabling Process to their specific organizational settings.