A methodology is presented for developing and testing plasma chemistry mechanisms needed for numerical models of microelectronics processing technologies. This includes a description of the types of data required for building a kinetic model, common sources for obtaining fundamental and kinetic data, suggestions for estimating kinetic parameters when data are not available, and approaches to validation and tuning of the model using diagnostic and sensor data. The approach focuses on the use of the CHEMIN Collection software for describing the gas-phase and surface reaction kinetics in high-density plasma simulations.