Billiards Using the Rails
Billiards is a game of geometry, of skill, of precision, and of practice, without all of these it is unlikely that you are going to be a very good player. Luckily for you here is a document specifically designed to teach you exactly how to approach some of the more confusing and complicated shots.
Many people are going to be overwhelmed by the prospect of kicks and banks, and when they get to trying for a double rail shot then they will probably already be read to give up. Playing of a rail is relatively simple as long as you know what you are doing.
Imagine that the cue ball that you are striking is nothing more than a ray of light and that the rail that you are aiming at is nothing more than a mirror. The cue ball is going to take almost the same trajectory that a ray of light would when hitting a mirror.
Though, you are going to have to account for drag, English, and velocity, each of this will offset the trajectory in varying degrees. To get a perfect rebound off the rail you need the perfect approach.
This means the perfect stance and the perfect strategy. Stand with your front leg out at a forty five degree angle turned out from the pool stick in hand, hold the stick lightly with your back hand almost near the butt of the stick, lean your head low so you can see the exact course on the table, and most of all aim for the exact middle of the cue ball.
Hitting too far to the left or the right of the cue ball is going to give the ball a spin that won't be noticed until it is caught on the edge of a rail. Usually when traveling in a straight line English isn't apparent and it only manifests once contact is made with a rail.
Hitting too far to the top or bottom of the ball is going to create a forward roll or a backspin. Again, this isn't going to be too disadvantageous on straight shots, but when dealing with the rails you have to be much more careful because this is going drastically effect the outcome of your shot.
Once you have the technique mastered then just imagining the cue ball as a ray of light being refracted by mirrors is going to be the easiest way to outline your shot. If that doesn't work for you, then you can always count the diamonds lining the outside of the table and create a mathematical equation hat will tell you where and how to exactly hit he cue ball.