Validation is the most incomprehensible part of developing a model. Nevetheless, no model can be accepted unless it has passed the tests of validation, since the procedure of validation is vital to ascertain the credibility of the model. Validation procedures are usually framework based and dynamic, but a methodical procedure can be followed by a modeller (researcher) in order to authenticate the model. The paper starts with a discussion on the views and burning issues by various researchers on model validation and the foundational terminology involved. The paper later highlights on the methodology and the process of validation adopted. Reasons for the failure of the model have also been explored. The paper finally focuses on the widely approved validation schemes (both quantitative and qualitative) and techniques in practice, since no one test can determine the credibility and validity of a simulation model. Moreover, as the model passes more tests (both quantitative and qualitative) the confidence in the model increases correspondingly.