Metal nanostructures are known to enhance various optical properties of objects of similar or smaller dimensions placed in their vicinity. Enhancement has been observed in laboratories, but theoretical understanding of the phenomenon has been for the most part relying upon the time consuming numerical simulations that reveal little physics and offer no easy path for optimization. In this talk, I intend to explain in simple terms the effect of optical enhancement by single or coupled metal nanoparticles. Specifically, I present an analytical model to describe the enhancement of various optical processes, to explain the luminescence quenching effect, and to establish limits of attainable enhancement. This analytical approach has advantages over numerical procedures by exposing underlining physics and by outlining a quick and direct path for optimization.