Pocket Sniper Snooker. The magic training tool.
Ghostball-Method
The Pocket-Sniper is a training device for aiming, that stays on the table during a practice shot without interfering the roll of the balls.
The Pocket-Sniper is aligned to the pocket using the long black center line and the black arrow, whereas the white circle represents the cue ball and the blue semicircle represents the object ball.

It is necessary to shoot the cue ball directly through the center of the white circle to succeed. The short black line, at right angles with the center line, stands for the way the cue ball takes when played as a stop-shot (no rotation of the cue ball on contact with the object ball).
3-Cut-Aiming-Method
The theoretically infinite number of angles for cut shots in the range of 0-90 degrees is reduced to three standard angles.

If the cueball lies in the extension of a coulored line, you are faced with one of the following standard shots:

Throughout intense training of these situations you can handle them. If you are faced with a shot you are able to see now, if it's one of these standards or you have to aim a little fuller or thinner on the object ball.
The blue line (representing the 1/8-Ball-Hit) is to practice thin cut shots.