Remain composed and concentrate on the beat; don't hurry. You will improve your sense of timing with practice. Make sure you catch the ball before it hits the ground. Don't let any of the balls escape your grasp; treat them all equally.
You can keep the ball in the air by simply tapping or clicking on it. Juggling numerous balls at once is the actual problem. Achieving a high score means staying focused and beating for as long as possible.