Dexterity is the skill of doing tasks with your hands. As a ninja this is very important and should be well refined. By increasing your dexterity you can unlock much more of your own potential. Skills you never image possible become a reality. One good way of training is to throw a small object up a small distance then grabbing it with the other hand. Try to steadily increase your speed as you go to make it a real test of skill. You should also try and incorperate some variations of movements as you go. Grab it from all angels not just from the front or bottom, but also the sides and top of the object. Another method is to tie a small soft object at about shoulder level. Set it in motion and try to strike it. You should again try to build up speed as you go and mix up your movements. The faster and harder you strike the more difficult it will become and will serve to quickly boost your dexterity. One more method I believe you will all enjoy is picking up an instument and playing it. You'll be surprised how much this will help improve your dexterity. From piano to guitar you need to move your hands and fingers which serves as good exercise and is a fun way to train.