Play some reggae music and bounce to the beat to get a feel for the rhythm.
Bend your knees, keep them relatively close together and rock them to the right, then left, then right, and pause at the right. Repeat starting left. The movement should be very smooth and in time with the beat.
Repeat this combination, but when you reach the third side in each combination, raise the leg of the side you land on, keeping it bent. For example, starting right, you bend your knees to the right, to the left, then lift your right foot from the floor, keeping it bent and angled to the right.
Return the right foot to the ground and bend your knees to the left, then to the right, then pick up the left foot from the floor, keeping the leg bent and angled to the left.
Repeat this combination, and, as you get comfortable with the movement, exaggerate the movements some more. Bend deeper, and when you raise the leg, pop your hips forward as well.
Add your arms to the combination. Swing and twist them in time with the legs. When you raise the leg and pop the hip forward, press the arms back to help accentuate the movement and exaggerate the shifting of your weight.