I believe the jab is the best tool in boxing, its sets up all your punches and it helps you find your range. The first punch you learn in boxing is the jab because its the bread and butter for this fine art.
Every time you throw the jab you must look directly down your arm once the punch is fully extended. By looking down your arm you’ll ensure that you’re well protected because your shoulder will protect your chin from getting punched. You must push of the back foot to transfer your weight into the punch and the knuckles must be turned over during connection.
The jab will set up all the other punches, most combinations usually start with a jab. Its been said that great boxers can win a fight by just using their jab. The jab can be fast or powerful, its important to vary the jab to keep your opponent guessing, every time you throw the jab your giving your opponent something to think about. Get practicing your jab and you will improve your boxing, start throwing jabs on the heavy back for 1 minute intervals with 30 sec rest.
Make sure your looking down your arm the entire time and bring the hand back to the chin every time, while pushing of the back foot.