Switch on autofire, or repeatedly press the fire button and the result will be that your keeper will save the ball every time.
Keep pressing the 'R' key when you take a penalty, this will show you where the players going to kick the ball.
In mid-match press all the function keys from left to right 'F1' to 'F10'. "S12" or "S14" should appear in the top right hand corner. You will now be able to substitute the computer's keeper and the new guy will be completely useless.
Substitute the opposing goalkeeper twice and he will not save your shots.