Paper provides in depth review of software and project estimation techniques existing in industry and literature, its strengths and weaknesses. Usage, popularity and applicability of such techniques are elaborated. In order to improve estimation accuracy, such knowledge is essential. Many estimation techniques, models, methodologies exists and applicable in different categories of projects. None of them gives 100% accuracy but proper use of them makes estimation process smoother and easier. Organizations should automate estimation procedures, customize available tools and calibrate estimation approaches as per their requirements. Proposed future work is to study factors involved in Software Engineering Approaches (Software Estimation in focus) for Offshore and Outsourced Software Development taking Pakistani IT Industry as a Case Study.