Heracross is very good at that game! When it's your turn, you want to aim for shortcuts and pick big numbers. When it's Heracross's turn, you want to block them from shortcuts and pick small numbers. But if you're too predictable, your opponent can take advantage, too.
Being good at the game involves sort of figuring out how each Pokemon plays, since they all have different strategies! Some of them are predictable, some of them are more cautious, and some of them specifically plan ahead to counter what you'll throw.
As a last resort, some people say if you have very fast reflexes, you can see the number they threw and throw a split second after them! But you have to be very quick.