Technical Abstract: Use of agricultural system models in field research requires a full understanding of both the model and the system it simulates. Since the 1960s, agricultural system models have increased tremendously in their complexity due to greater understanding of the processes simulated, their application to real world problems, and acceleration of modern computing power. As a result the parameterization of a system model is now more complex, requiring more input variables and providing more outputs to verify. This chapter provided a protocol on how to parameterize the USDA-ARS, Root Zone Water Quality Model (RZWQM2). It summarized input data requirements of soil, weather, and plant as well as minimum data needed to calibrate the model. Calibration of each component or process was illustrated along with possible adjustable parameters. An iterative procedure for model calibration was also emphasized in the chapter. Difficulties in model application were presented along with possible solutions. However, the steps for model calibration were still in the trial and error mode and can vary from application to application. Model users should benefit from the materials in the book chapter by combining them with those in the RZWQM2 user manual released with the model.