This paper attempts to provide a general guideline to develop a practical model for MOSFETs in the sub 0,1 μm generations. It starts by giving an overview of the different modeling approaches and options including charge based approach, surface potential based approach, and conductance based approach. Their relative advantages and weaknesses will be discussed. The evolution of the BSIM models from its first generation to the most recent release will be used as an example for the development of a practical device model. It will be followed by a discussion on how the accelerated technology development may impact the traditional modeling approaches. A new paradigm to incorporate modem software engineering methodology to shorten model development cycle will be presented.