This is more a hint than a cheat, but to win in Fifa 12 easily, simply go into options, then CPU customization. From there, enter the following values:

Speed: 0
Acceleration: 0
Shot fail: 100
Pass fail: 100
Shot speed: 0
Pass speed: 0

Now, go to user customization and enter:

Speed: 100
Acceleration: 100
Shot fail: 0
Pass fail: 0
Shot speed: 100
Pass speed: 100