Keep your elbow close to your body
The most important part in positioning for a jab is to keep your hand high and elbow close to your body. People often undervalue the importance of keeping elbows close to their bodies and this not only reduces the power of jab but at times, it can also imbalance them. Note that you are not required to stick your elbow to the body but it should be really close in.
Push your back foot
After you have positioned your arms properly, it is strongly advised that you move one foot to the back and push it like a pitcher. People often misunderstand the concept of boxing as they believe that the strength just comes from the arms but in fact it comes from your body. You must stand firm on the ground and try to keep your body as balanced as possible.
Extend your arm
Now you must move your other foot a little forward and try to extend your arm towards your target. It is important that you should estimate the distance between your arm and the target carefully, otherwise it will be a waste of your efforts and you might end up getting a jab from your opponent.
Rotate your fist
While throwing a jab at your opponent, you must rotate your fist clockwise, making sure that your thumb goes inward before that.
Move your chin downwards
You cannot stay open and exposed to your opponent while throwing a jab at him/her and it is important that you should drop your chin to your shoulder.
Build coordination between your hands and toes
There must be strong coordination between your toes and hands. You must practice to build this coordination.