Moving your hips in big circles at a slower pace will work better than faster, smaller circles.
If you're having trouble catching the hula hoops the Miis throw at you, try lifting your right or left foot while the hula hoop is coming at you. The goal is to shift your weight to the side the hula hoop is being thrown from.
You may notice a reaction delay when you lean in to catch a hula hoop. Try leaning a moment earlier than seems necessary to compensate. This might result in fewer spins in the short term, but simply catching the hoop will result in many more spins long term and a higher score