Your jab is your most important punch. It's not necessarily your most powerful, but it is your most important. Defensively, it helps keep pressure on the other guy, and off of you. Offensively, it's a great set up for other punches off either hand.
To put some weight in your jab, you can do a very simple thing - lift your back heal. Doing this helps you transfer your weight forward when you step with your lead leg as you jab.
You can see a video demonstration of this on my Youtube channel - NewYouKungFu. Here's it is.
A Little About This Blog . . .
I've been involved in martial arts since 1973, and owned a Kung Fu, Tai Chi and Kettlebell Gym for 24 years. Now I work online full-time, teach Corporate Workshops, and write both fiction and non-fiction.