Glass is simple... You set refraction level at 1, reflection level somewhere between 0,5-0,9, diffuse level to 0 and then you are done... (IOR is defaulted at glass)
Mirror and other metal materials might be sometimes tricky... The key is to use very low diffuse values (very dark gray, but never 100% black) Also, never use reflection level of 1 for metals, use from 0,55 for aluminium and such, up to 0,95 for mirror and such, depending on how shiny they are, and use high fresnel IOR value.
So for example:
Brushed steel:
Diffuse - RGB 5,5,5 (dark gray), reflectivity 0,7, fresnel IOR 10, reflection glossiness 0,4
Mirror:
Diffuse - RGB 3,3,3 (very dark gray, nearly black), reflectivity 0,9, fresnel IOR 20, reflection glossiness 1
