I'd recommend you to look up at some tutorials in the tuorial section on this site:
http://www.gfxvoid.com/forums/forumd...ture-Tutorials
You could also look on Deviantart for some good signature tuts.
I started by following these tuts step by step, ending up with some cool results.
After following enough of those tuts you should be able to work with several techniques (like light and shadow)