We review recent developments in experiment, simulation and theory with an eye towards highlighting salient aspects of shearing and failure of granular materials under quasi-static loading. The exchanges and flow of energy within the deforming medium manifest themselves in the evolving kinematics and contact force distribution. As such, we focus on particle motion and the evolution of force chain networks, particularly within shear bands and under conditions that generate stickslip behavior. A common goal is to reconcile theoretical descriptions of these dissipative processes at different length scales and to relate these to simulation and experimental observations. Implications and challenges brought to the fore for micromechanical constitutive theory are centered around the dominance of nonaffine deformation and force chain evolution across multiple length scales, from the particle to the bulk.