Credit: Game Genie Code Manual
Programming Your Own Codes
When programming your own codes, keep in mind the following guidelines:
Your success in code programming will depend a lot on luck. Keep trying! Of course, some of the effects you create you may not like. Alm0ost any effect is possible-good, bad, interesting, annoying, fun, or just plain silly.
If a code you program interrupts the game or causes an undesired effect, just turn the power off and then on again, and the program different codes to play.
How to Program
There are two basic methods used to program your own codes by changing existing codes.
Using Method #1, you change the 6th character of the code.
Using Method #2, you change the 1st and/or 2nd character of the code.