Of the forces commonly encountered when solving problems in Newtonian mechanics, introductory texts usually limit illustrations of the definitions of conservative and nonconservative forces to gravity, spring forces, kinetic friction and fluid resistance. However, at the expense of very little class time, the question of whether each of the common forces is conservative or nonconservative can be settled once and for all. I provide here brief arguments for classroom use that establish the conservative or nonconservative nature of each force commonly encountered in mechanics problems, including forces whose conservative or nonconservative natures are seldom or never addressed by textbooks.