Objective: To provide an analysis of stimulation parameters for deep brain stimulation (DBS). Methods: Synthesis of theoretical and empirical findings is used to provide guidance for the selection of stimulus parameters. Finite element modeling is used to investigate the effects of contact location and electrode geometry on the electric field, and to estimate the effects of current density distribution on the limit for non-damaging stimulation. Results: Anatomical targeting of DBS electrodes is complicated by the uncertainty of which neural elements are targeted and differences in the electric field distribution in fiber tracts and nuclei. Electrical targeting by selection of electrode geometry and stimulus waveform can alter the distribution of the electric field and control neural activation. The recommended charge density limit for DBS represents a liberal estimate for non-damaging stimulation. Short duration stimulus pulses reduce charge injection and increase the therapeutic window between therapeutic effects and side effects. Conclusions: There are several challenges to developing rational methods of selecting stimulus parameters including a large number of degrees of freedom, the unknown effects of stimulation, and the complexity of the responses. Significance: Understanding the fundamentals of electrical stimulation of the nervous system enables rational selection of stimulus parameters.