This document provides an overview of ionization theory, API-MS hardware, considerations for samples and solutions, interpretation of API-MS mass spectra, generation of structural information, inlet considerations, troubleshooting, and methods development. The course is designed for undergraduate chemistry students with experience in mass spectrometry, including mass spectrometer operation and EI data interpretation. It is also suitable for LC/MS operators or supervisors planning to use LC/MS, GC/MS operators or supervisors planning to utilize LC/MS, and individuals experienced in LC separations who plan to use MS detection. The course includes practical exercises in API-LC/MS methods development and spectral interpretation.