The following tutorials are also very useful in learning how to mod gsc files on Call of Duty. Make sure to check them out if you don't understand something. Also remember to read some code inside .gsc files to see how certain stuff is done, it works super well for learning purposes. 
W@W Basics, Variables & Operators:
http://www.moddb.com/tutorials/scripting-1-basics
http://www.moddb.com/tutorials/scripting-2-variables
http://www.moddb.com/tutorials/scripting-3-operators
MW2 Program Flow, Functions, Variables, If Statement, While Statement, Switch-Case-Statement:
http://www.se7ensins.com/forums/threads/tut-basic-gsc-scripting.192492/
http://www.itsmods.com/forum/Thread-Tutorial-GSC-Modding-Tutorial.html
CoD4 Tips, technics and examples:
http://www.thetechgame.com/Tutorials/id=2134/how-to-gsc-mod-call-of-duty.html
BO modding beginners (+ scripts, dvars & weapons):
http://www.itsmods.com/forum/Thread-Tutorial-Gsc-Modding-for-Beginners.html
General Scripting Guide:
http://www.ugx-mods.com/wiki/index.php?title=Scripting_Guide
Enjoy
W@W Basics, Variables & Operators:
http://www.moddb.com/tutorials/scripting-1-basics
http://www.moddb.com/tutorials/scripting-2-variables
http://www.moddb.com/tutorials/scripting-3-operators
MW2 Program Flow, Functions, Variables, If Statement, While Statement, Switch-Case-Statement:
http://www.se7ensins.com/forums/threads/tut-basic-gsc-scripting.192492/
http://www.itsmods.com/forum/Thread-Tutorial-GSC-Modding-Tutorial.html
CoD4 Tips, technics and examples:
http://www.thetechgame.com/Tutorials/id=2134/how-to-gsc-mod-call-of-duty.html
BO modding beginners (+ scripts, dvars & weapons):
http://www.itsmods.com/forum/Thread-Tutorial-Gsc-Modding-for-Beginners.html
General Scripting Guide:
http://www.ugx-mods.com/wiki/index.php?title=Scripting_Guide
Enjoy
