Milo just about said it all.
The only thing I can add is a method of getting your finger "programmed" to take the pictures that you want. This trick helped me and it might help you too.
Get a brightly colored ball the size of a baseball and a friend who won't think you've gone out of your mind and practice. Have your friend hold the ball at arms length about 30 feet from you. Your friend should then call out "ready". Once he's called ready he should count down, silently, to zero from any number between 5 and 12. At zero he releases the ball.
While your friend is doing all that you should first depress the shutter release button to force the camera to prefocus on the ball. Then when he releases the ball depress the button the rest of the way to take the picture. The object of the exercise is to photograph the ball before it hits the ground. Once you can do it 8 times or more out of ten you're ready to try it out on the flying field.
Ken