Ensuring semantic interoperability in international studies is crucial. In this context, the mapping of national to international vocabularies is necessary. The Standardized Vocabularies of OHDSI provide such a mapping, which forms the basis for semantic interoperability in the standardized data model OMOP CDM. The aim of this paper is to provide a guideline for vocabulary mapping that supports developers in efficiently implementing the technical application of mappings into the ETL process for transforming data to OMOP CDM. By implementing materialized views and creating a decision tree, we provide a solid foundation for efficient semantic mapping in OMOP CDM. With our work, we mark an important step in realizing international observational studies based on OMOP CDM.