1. Open up the keyboard
2. Trace the letters back to the pins
3. Note the pin layouts and shift registers
4. Attach the wires
For more info:
http://www.instructables.com/id/Hacking-a-USB-Keyboard/
http://www.extremetech.com/article2/0,2845,1656176,00.asp
http://www.modd3d.com/articles/item/keyboard-hack
