id suggest buying a book on the basics.., no sarcasm meant but if you dont know the answer.., best do some hands on learning.., i mean even the movies at the maya stat up explain shading.
see if you can find a cheap one.., even maya 4.., the priniples are not really different unless you are doing advanced shading, which at theis stage you are not.
good luck
take it easy and life will be easy