Bend your leg back at the knee, and swing your foot forward, brushing the ball of your foot against the floor. A brush can also be done to the side or to the back---just make sure as you swing your foot out, the ball of your foot hits the floor.
A ball change is just a step with each foot, with all your weight on the balls of your feet. It is a step that is often added on to the end of another step---for example, you could do a brush, then a ball change. Which foot you step with first will depend on the steps that come before and after.
One foot at a time, put all your weight on the balls of your feet, so your heel is up in the air, then drop it to the ground. Think of this step as though you are walking in place, without ever lifting your toes off the ground.
Once again, think of this step as though you are walking or marching. Bring your foot up, step down just on the ball of your foot, then drop your heel.
A heel tap is the opposite of a step heel, and it is actually the most similar to a normal walking movement. Lift your foot up and place it down so you are leaning back with all your weight on your heel, then drop the front of your foot.
Brush the ball of your foot on the floor, then step down with your entire foot. This step is a combination of a brush step and half of a ball change.