Mixing up the number of jabs executed is very important
therefore pracrice single, double and triple jabs.
Practise power jabs, by feinting with the right hand.

Practise all the possible defences for the jab including
blocking, slipping, bobbing and weaving etc.

Learn to counter a jab with a jab.

Of all the punches, the left jab is likely the most important. And it is possible to win fights with just the jab, and good balance, footwork
and defensive skills.