In the recent time, the main subject of many research studies is renewable energy due to its positive contribution to the environment and sustainable society. Integrating Distributed Generators (DG) which are driven from renewable energy sources (RES) can lead to increased efficiency and improved performance of most distribution networks, and can make contributions to evolve power networks into Smart Grids. On the other hand, DG penetration results in some operational challenges due to their intermittent nature. The list of problems includes voltage limits violations and thermal overloading problems, protection systems failure and power quality deterioration. Therefore it is essential to determine the proper size and location of DG needed for the integration without inducing such problems. In order to obtain an appropriate analysis of safe and efficient DG integration without breaching in system operation, the content of Hosting Capacity (HC) is introduced. HC enhancement is considered as beneficial for distribution networks, and HC improving techniques has been broadly discussed and studied in the last decade. This paper presents a comprehensive review on the studies of HC, its concept and definitions, effects on distribution systems. HC improving methods are discussed in the paper by analyzing the impacts of DG integration on power systems. The paper also compares HC enhancement methods and suggests the best option based on performance indices of each method.