Simple exercise. Ask a friend to drop things (in this case a leaf) and practice trying to catch it. You’ll want to use a high shutter speed, at least 1/1000th of a second, and to make the game harder, a narrow depth of field, maybe even wide open (f1.4). You’ll have to pre-focus and lock focus on the spot that where you expect the object to be (use your friends hand) and then have them count 1-2-3 drop and click when ready.
Once you’ve mastered this, think about the angle you’re shooting at and play with that a bit.
And then try and do the exercise without your friend giving the 1-2-3 warning. The exercise gets you into the practice of pre-focusing, as well as being quick on the trigger. It isn’t very different from the wild west trick you see in the movies where a coin a thrown up and the gunfighter shoots a hole through it. In fact, if you have something larger than a coin that can be tossed, you can practice the wild west trick as well though you are going to have to focus on the object while it falls.