From the beginning of supercritical water oxidation ( SCWO) research in the early 1980s, mathematical models have been used to correlate, predict, and explain experimental reaction kinetic data. Initially, these were simple global rate laws, involving only a single overall reaction or a few reactions, each with its own arbitrary rate law. As computational power increased and the library of elementary reactions from the combustion literature grew, it became feasible to construct elementary reaction rate models, which are a more accurate means of representing the SCWO process. Early efforts to construct elementary reaction rate models resulted in very poor agreement with experimental data unless model parameters were adjusted to optimize the fit. However, today with considerably more computing power and a more robust collection of elementary rate parameters from the combustion literature, rate predictions in the relatively low-temperature, high-pressure SCWO environment are more effective and accurate. These enhancements make it possible to build models that hold the predictive capacity to help guide experimental design and gain a greater mechanistic understanding. This paper details current best practices for the construction of these elementary reaction rate models, including selection of a base model from the combustion literature, identification of possible intermediate compounds, and estimation of unknown rate constants by ab initio calculations or analogy to known chemistry. A set of model compounds was selected to illustrate rate modeling approaches for both oxidation and hydrolysis pathways.