Requirements Engineering (RE) is one of the important disciplines of software development. With the passage of time, software development process changed from traditional approaches to agile approaches. RE techniques also changed from traditional software development to agile software development. Research shows that the traditional software development can't handle rapid change in requirements while the agile approach can handle rapid change in requirement during and after the software development. In this paper an overview of RE followed by different software development project is reviewed. Also a unique model FlexREQ to handle RE approaches though Dynamic Link list (DLL) and an Entity Relation Model (ER Model) is discussed. © 2012 IEEE.