In this manuscript, a methodology is presented for designing robotic arms for service tasks. This methodology attempts to take into account analytically the specific novel requirements that are needed for service tasks. This goal is achieved by means of the formulation of specific objective functions which can evaluate and compare the quality of a design among others. Additionally, these objective functions are investigated for being implemented in suitable optimal design algorithms. The proposed methodology can be extended to any robotic mechanism for service tasks. The design method begins with the development of type and number synthesis to identify the minimum needed number of degrees of freedom. After selecting the most suitable mechanism, the proposed design procedure uses the objective functions to compare the most acceptable solutions. Finally, by means of a numerical algorithm, the dimensional synthesis is performed to obtain optimal length and thickness of each link. The proposed procedure has been applied for a case of study in order to prove its feasibility and practical usefulness.