A Beginners Guide To Hacking Games

You Need:
A program such as PC Tools
An infinite ammount of patience

What to do:

Pick a file, any file (okay, okay. Make that a savegame file)
Back up the file you intend to hack.
Select the file.
Start the Disk Editor (on PC Tools).
Look through for common bits of code.
Do something different in the game and save again under a different name.
Look for bits of code that have changed.
Come to the conclusion that you don't understand any of it & go read the manual.
Realise that the manual's even worse.
Give up & use something you got from the web.