This cheat requires really fast autofire, but you may be able to emulate it on a joystick/pad by pressing the fire button really quickly. During play, if you line up the man where you want, and then press down the autofire, it will generally throw the ball down the center of the lane. The less force there is, the closer to the center of the lane the ball will be bowled. If you put your man to the far right, and put the speed up to almost full force, you can generally bowl a perfect strike. Its a very useful technique.
Also, if you have a single pin left, or a similar situation in your game, then this is an excellent technique to line up the ball.
NOTE: This cheat will not guarantee a strike, or spare every time.