Try staying as relaxed as possible. Feel the movement. Do it smoothly. Dont worry about dropping the ball. Be smooth with your movement, theres always plenty of time after you flick the ball up, all you have to do is turn and land it! And one important thing to keep in mind is,
Dont flick the ball up as soon you get under it! Flick it up when the ball is comes down so that you can force it to go straight up. This works for me

Good luck.