A small light tap is one of the easiest and most basic embellishments, and is a nice way for the follower to mark and express the double-time ('quick, quick') - or the 'and' count in between the beats - while the leader is leading a step on the whole beat ('slow'). A tap can be done in the middle of virtually any step - back, side, forward, ocho.

At the mid-point of the step, as your free foot brushes past your standing foot, tap your free foot against the ground. Do it with just the ball of the foot, with the foot tipped slightly towards the metatarsal/big toe edge (this poised foot placement is the common aesthetic of tango).

Make sure you still arrive into the next step led by the leader on the whole beat. Also be sure that after you tap you keep stretching your leg back straight into the next step. Do not undercut yourself and step shorter than the leader.

Variations

Foot Placement:
-Tap right next to the standing foot.
-Tap slightly to the side of the standing foot, with the knees still close together and the free leg slightly flexed and angled out from the knee down.
-Tap further out to the side, with the free leg straight so the knees are further apart.
-Tap with the heel instead of the toe, with your foot highly flexed.

Emphasis:
-Tap heavy into the ground with the emphasis on the downward strike.
-Make the tap lighter, even letting it bounce up a little, with the emphasis on the 'up'. (Imagine that the ground is hot and you have to pull your foot away from it quickly to keep from burning it).

Tempo:
-Try to make the move extra staccato and 'freeze' your foot for a moment in place as it taps. Hold your foot in the tap position for as long as possible before you need to move it again in order to arrive to the next beat on time.
-If you are really fast, try doing a double tap in place between steps.

Exercises for Home

-Walk forward and back towards and away from a mirror, with music, practicing the tap.
-If you have space, walk backwards either counter-clockwise around a room or down a hallway with no obstacles, practicing the tap and making sure doing the tap does not make you change your proper posture and technique of taking back steps. Try it to slow music and to faster music. See how the music you are listening to might inform the movement your body produces.

Exercises for the Bus Stop or Grocery Line

-Standing in place on one foot, tap the other foot next to it. Try doing it really fast, making sure your foot is poised. Try the different variations above, doing them repeatedly in place. Make sure your weight is settled down through your standing leg and the hip of the free leg is not lifted, but relaxed towards the floor.