Lie a drill ladder on the ground.
During this exercise both feet will go in the ladder, then both feet outside the ladder.
Start to one side of the ladder.
Place your nearest foot in the square, then bring your other foot inside.
Step your first foot to the other side of the ladder, then bring your second foot to join it.
To step back the other way, step your first foot across the second into the next square, then bring your second foot to join it.
Step your first foot to the original side of the ladder, then bring your second foot to the same side.
Repeat this sequence.
Start off steadily, picking your feet up off the floor quickly and landing on your toes.
Build the speed with each length.