Slopes in open pit mines must be considered as geotechnical structures. Therefore their design and implementation must be conducted with all consideration including technical, economical, environmental and safety issues. But these structures are above all natural geological and geomechanical features and the geological structures as well as the petrographical nature of the rock material control the deformation and failure mechanisms. It is therefore important to implement a well-defined methodology which should be conducted according to the following phases: 1) rock mass characterization derived from the acquisition and analysis of geological and geomechanical data; 2) determination of the potential mechanisms of deformation and failure, and their numerical  modelling; 3) slope design and definition of reinforcement and monitoring methods. This paper presents various available techniques and tools to achieve these successive phases and illustrate their implementation and also limitations through case studies of slope design in open pit mines.