There are approximately 4 or 5 aiming techniques in common use, and another 3 or 4 more esoteric choices. The easiest to understand and the most commonly used aiming technique is also the simplest to learn - the "ghost ball" technique.
The concept is simple. If two object balls were perfectly lined up to the pocket, all you need to do is shoot straight at the first ball and the second ball will go into the pocket.
To aim at the object ball, just imagine the first ball (a ghost) is in perfect position as the example above, and shoot straight at the ghost ball to make the object ball.
That's all there is. Align your body up on the line from the object ball to the pocket. Use your imagination to drop the ghost ball into position. Walk back to your cue ball and set up for the shot. Keep your eyes on the ghost ball (so it doesn't disappear on you). When perfectly aligned, shoot straight at the ghost ball. The only reason to miss the shot would be because you imagined the ghost ball in the wrong position.
Get the Book!! $7.00
PDF book (good for smart devices) (Includes my Money-back Guarantee)