There is a Fresnel Reflection (pronounced fray-NELL) slider in the reflectivity section of the Advanced Material Editor. This setting increases the reflectivity of surfaces at glancing angles. It does not alter the reflectivity of materials at perpendicular viewing angles. Turning this setting down may offer more control when only slight reflectivity is desired.
The Fresnel slider is on the Advanced material editor. It will have more effect on objects which are less reflective, than on objects which are more reflective.