I won't try to give too much specific advice, because every person's physiology is a bit different. But to enhance your feel for striking with the ball/instep of your foot, run hills.

More and more hills.

When you do so, "commit your body" to the hill--meaning, lean way forward (into the hill) and project in the direction you want to go (parallel to the ground). Basically, you apply force through the balls of your feet & toes so you do not bounce, but move in the direction you're going.

After you run lots of hills this way, when you run on flats, try to project forward--that is, apply power forward instead of into a bounce. Typically, when you do this, you will naturally roll your body forward a bit and land on the front half of the foot.

This is all hard to explain...a running coach would do a fantastic job helping you.

BTW -- if heel-striking is really a habit you're looking to break, as you very well should, try running barefoot in grass sometime. And spend more of your day barefoot if possible. Being barefoot will help develop relevant muscles; running barefoot will help you with the form I tried to explain above.