Summarize the following:
Take your normal stance and prepare for your run-up. Position your index and middle fingers to either side of the middle seam. Your thumb should be to the inside of the same side of the seam as your pointer finger.  When gripping the ball to throw a fast ball, the joints of your fingers should wrap around the contour of the ball to hold it away from the palm of your hand.  Don’t let the yorker’s reputation as a difficult throw put you on edge. Relax. Take a few breaths. A smooth, consistent throw will improve accuracy. Really narrow your focus on a feature somewhere around the batsman. Fix your gaze on the crease line or the base of one of the stumps. You might even find it useful to focus on a feature of the batsman, like their toes. Lock your eyes here for the duration of your delivery.  By training yourself to focus on a particular point, you’ll limit variables that could affect your delivery. This will allow you to devote more attention to other areas, like form. An ideal yorker will land as close to the batsman as possible while still bouncing before crossing the crease. Envision yourself completing this throw to improve accuracy. Slowing things down a bit might be just what you need to nail your target. But the opposite can also be true. Try a slower and quicker than normal pace for your run up when bowling a yorker. Test each to see which works best for you. In some cases, your normal bowling speed might be your most accurate pace. Accuracy is everything when bowling a yorker. The motion for throwing a yorker is much the same as a normal fast throw, but the shoulder of your bowling arm is especially crucial when delivering a yorker. While delivering, drive your shoulder in the direction of the bottom of the stumps. Driving with your shoulder will improve the fullness and speed of your yorker. Take time to practice this motion intentionally. Try to get as close to the batsman as possible. Ideally, the ball will land right before the batsman’s feet. This provides little time for him to dig out the ball and hit it into play. Place your feet so you are well balanced at the moment of release. Doing so will have a positive effect on your accuracy. Small adjustments can make a world of difference. Try to only adjust one aspect of your throw at a time so you can isolate and improve problem areas. Have a coach or a teammate watch and comment on your form. Record a video of yourself throwing yorkers on your phone. Compare this to YouTube videos of yorkers thrown by cricket professionals. Imitating the pros might improve things.

Summary:
Hold the ball as you would a fast ball. Take aim. Adjust the pace of your run-up. Drive with your shoulder as you throw the ball. Throw the ball so it lands close to the batsman. Practice frequently and adjust your form as necessary.