In your graal folder, there is a document called npcprogramming.doc. You should read this first, and experiment with the commands. This is the basis of graal script, and is known as GS1 (Graal Script 1).
However, graal script has advanced into GS2 (Graal Script 2). This link should help with that:
http://ilfirin.org/graal/GScript
Also, if you are learning graal script a key element to success is to be very experimental, with the support of an advanced scripter. Therefore I recommend you get hooked up to the #gscript IRC channel, where you can ask experienced scripters questions.