Your best bet is to go to the A/W site...there's a great tut. there on making realistic glass. Once you understand what and why it's done that way, then you can feel confident to go ahead and mess with your own settings
Red bellows of flame have blackened my stones
Convulsing my frame and cracking my bones
Hell's dragons of steel who roar in their chains
Crawl into my caves to suck out my veins.....
-The Mountain P.F.M.