The Generalized Algebraic Modeling System (GAMS), developed by Alexander Meeraus, Anthony Brooke et al., is a language for expressing mathematical models in a form that is both easily understandable to a modeler and processible by a computer. For practitioners and researchers, it can greatly reduce the time required for formulating, documenting, solving and analyzing large, complex linear, nonlinear and integer programs. For teachers and students, it is a valuable tool for learning advanced modeling. This paper is a tutorial for the beginning GAMS user. Keywords: Optimization, Modeling languages, Mathematical programming, GAMS, Computer programming, Programming languages.