Cuban motion begins with how you use your feet. Notice that your leg will straighten if you take a step leading with your heel. If you step to the ball of your foot, your knee will naturally bend. In rumba, the ball of your foot never leaves the ground. Practice walking on the ball of your foot by sliding your foot along the inside of the ball as it moves and push into the floor as you step.
The hip motion is a result of the bending and straightening of the knee. Stand with your feet together but the toes pointing slightly outwards. Bend your right knee and keep the knee pointing straight forward as it bends. The trick is to keep the weight over the bent knee. You will notice that the right hip drops and the left hip is up and back. Switch by first pressing down into the floor with your right foot. Press until your right knee straightens. The right hip will start to rise and be even momentarily with your left hip. The left hip will drop, bend the left knee and allow the right hip to go up and back while your weight shifts to the left leg. Continue to switch right and left in this position. The same exercise can be done with the feet slightly apart. You will see the connection between the knee action and hip action as you switch.
The next step is to combine walking with the hip movement. Move side to side. Start with your feet together and take a step to your left side. As you take your weight on the left foot, the left knee is bent and the left hip is dropped. Straighten the left leg by pushing down into the floor. As the leg straightens, the left hip will rise and the right hip will start to drop. As you take your weight onto the right foot, the right knee should be bent and the right hip dropped all the way. The left hip will be up and back. Continue to practice walking side to side in both directions.
The key in American-style Cuban motion is to take the weight onto a bent knee. Remember that the motion comes from the floor up, and think of the body as a chain of reactions. First the foot, then the knee, then the hips.
Because the weight is always over the balls of your feet, your posture will be forward as well, and it may feel like you are tipping forward. Sway from the balls of your feet back to your heels, and then back to the balls of your feet again. This will help you get familiar with where your weight needs to be. Always keep your stomach muscles engaged by pulling your belly button in towards your back, and do not allow your lower back to arch. Practice this position by standing with your heels against the wall and flattening your lower back against the wall. Check your posture by trying to slip your hand between the wall and your back.
Rumba is danced in the closed dance position, and you should be standing directly in front of your partner, not offset as you are in the smooth dances such as waltz and foxtrot. The leader places his right hand on the follower's left shoulder blade and holds his elbow up forming a shelf for the follower's arm. The follower rests her left arm lightly on the shelf and places her hand on the leader's right shoulder. The follower's right and the leader's left hand rest gently together with the elbows bent at a ninety degree angle. Try walking forward, back and side to side using Cuban motion with your partner.