Have you ever missed your shape and ended up frozen against the rail or another ball with the object ball 3/4 of the way down the table with a difficult angle to the pocket? This is a sure end to most runouts for the average player. I have learned 3 techniques over the years that help me with these type of shots. I still miss some of them but I now make a lot more than I miss. First of all it should be common sense that you don’t shoot these type of shots with a hard stroke. Keep you stroke in the soft to medium range to maintain your accuracy. The biggest reason these type of shots are missed is because the tip of the cuestick bounces off the cueball unless you shoot very softly.
There are 2 techniques to keep the tip on the cueball and minimize the deflection of tip after contact. The first one is difficult for me to use when I shoot over another ball as I have relatively short fingers. It does however work well when I shoot off the rail. Simply squeeze the shaft in the V between your thumb and forefinger (with the end of your forefinger rolled underneath) and keep it clamped down throughout the stroke. Make sure your hands and stick are clean as you may have difficulty stroking. You might have to use some powder to make the cue slide the way it should.
The second technique works pretty much the same except instead of applying pressure to the tip end of the stick apply it to the butt end of the stick. Many players have a loose grip which allows the proper wrist action to keep the cue in the plane of the shot. The problem with a loose grip when shooting off the rail or over a ball is that it allows the butt of the cue to deflect in the opposite direction of the deflection of the cue tip. If you grip the butt tightly (don’t choke the crap out of it) it can’t deflect which will help keep the tip in the proper position to complete the shot. When gripping the butt don’t grip it with all of your fingers. Only squeeze it with the ring that is formed with your thumb and forefinger as it wraps around the butt. By only gripping with the thumb and forefinger you will not impede the wrist action that is necessary to complete the shot. You can combine both of these techniques to keep your cue absolutely straight when you have to jack up or are stuck on a rail.
The last technique that works in conjunction with the 2 above is to make sure you don’t drop your elbow when you complete your stroke. Most people including me have a tendency to use their whole arm to complete the stroke when they are in an awkward stance. Make sure the part of your arm below the elbow is the only part that moves.
I’m sure that if you learn these 3 things your ability to make jack up and rail shots will greatly improve.