The purpose of this paper is to review the literature on reliability allocation and to propose a guideline to choice the most suitable allocation method, in respect to desired goals and available resources. The proposed review systematically analyzes allocation methods in literature, determining main features and the area of application. The choice of a reliability allocation method depends on several factors and, moreover, the considered design stage. However, in literature there is a lack of a comprehensive methods’ summarization, making it difficult to choose the most suitable strategy. New criteria for the classification are also highlighted. Furthermore, reliability allocation methods become ever more complex and accurate, in particular trough the employment of advanced mathematical tools. The paper contains a comprehensive analysis of frequently-used allocation methods and a proper summarization through various criteria. Additionally, it points out opportunities for future research.