The basic concepts involved in formulating and analyzing simulations of kinetic space plasmas are presented for readers with little background in simulation methods. Issues related to choosing the appropriate physics models and numerical algorithms, such as the correct representation for the plasma, proper description of the electromagnetic fields, geometric effects, initial and boundary conditions, and diagnostics, are discussed. Some of the strengths and limitations of the various approaches are also described. Explicit examples involving the simulation of collisionless shocks are presented to illustrate these points. Questions related to numerical accuracy and verification of the results are also examined and again illustrated through appropriate examples. ¿ American Geophysical Union 1996