Better still, visit
www.sealedgameheaven.com - You'll easily learn everything you need to from there.
SGH has a dedicated "official" VGA grading forum, where you'll learn all you need to know, plus also be able to see lots of examples of some very sexy graded video games!
Here's the link you'll need:
http://www.sealedgameheaven.com/inde...wwvggradercom/
(You may need to register first though)