Stones said:
The cut break is used mostly when players are restricted to breaking from the "box".
Most players I've seen use one diamond out from the side rail along the head string for the cue ball starting position.
If you are breaking from the right side of the rack, you use low right english. Just the opposite from the left side.
Stones
In addition to when players are restricted to the box, a player will often use a cut break if they're not getting good results from hitting the one ball flush. In other words, a world class player must be able to adjust his break to how the table is playing. Although I'm by no means anywhere near world class, I approach it this way: I generally prefer to break from the left side rail, but if I find I'm not getting the wing ball or the one ball to fall from there, I'll go over to the right side rail. If I'm still not getting results, I'll then break, hitting the one ball full, from the right or left side of the box, and if I'm still not getting results, I then go to the cut break.
To explain a little further, the cut break really increased in popularity with the advent of the break box, which was designed to prevent the high occurence of wing balls and one balls falling on the break. The ever inventive pros soon realized that by cutting the one ball they could still induce the wing balls and one balls to fall a reasonably high percentage of the time, but in order to get the cueball to the center of the table, they had to apply low outside. Thus, the cut break.
Despite the occasional usefulness of the cut break, I personally feel that hitting them square is generally the way to go. IMHO, there is no single shot in pool that can break down an opponent like a break that regularly has a report like a high-caliber rifle, makes three balls and scatters the rest to perdition, and jumps whitey back a couple of feet to squat dead in the center of the table. It can make a player abandon all hope!