The single thing that helped me the most using GC was to start using EZSkin to fix the shaders on my characters. Free here.

EZSkin 2 can also fix hair issues.

The other majorly important thing is for you to run Gamma setup on your monitor, so you are really seeing what is there. Most video cards come with a GC setup routine. If not, you can get close by using the chart at the middle of this page.

Moriador's advice about lights is bang on. IBL is old school. IDL is what works best given the new environment. If you want to use IDL outside, be sure and snag BB's envdome here.