When you throw a PokéBall at a Pokémon to capture it in Pokémon Go, you can increase your chances of catching it depending on how you throw. The white circle around the Pokémon determines the quality of your throw, and the ever-shrinking one inside determines the accuracy. If you throw your PokéBall inside the shrinking circle, you may receive a Nice, Great, or Excellent throw. Of the three, the excellent throw is the most difficult to achieve.
To get a great throw, you need to wait until the shrinking circle almost reaches the dead point of the larger circle. It creates a small icon in the center of the Pokemon, which makes it quite difficult to fatally hit. You can only achieve a great throw by having your PokéBall throw a land into the smaller circle, not waiting for the smaller circle to appear and then attempting to capture the Pokemon.
An early strategy of some Pokémon Go trainers was to wait for the circle to get extremely small, then remove their finger from their PokéBall. Unfortunately, you can't do that anymore and it resets it.
When the icon gets small enough, you throw your PokéBall at the one in front of you and hope it hits the icon. You'll know if he hit the smaller one because he'll get a notification and tell you if it was a nice, great, or excellent throw. You'll likely switch between a Large or Excellent roll, especially when trying to wait for it to get smaller.
A great way to rack up excellent rolls is to do so on more common Pokémon, such as those you encounter while walking around or hanging new PokéStops. It's much harder to do this against Legendary Pokemon and Research Task encounters. When you roll Excellent, it increases the chances of catching that Pokémon.
It takes a bit of practice to nail a great pitch. Due to the small size of the inner icon, this won't be easy, and you probably won't want to try when the target Pokemon is far away. Try to wait until you encounter a Pokemon that is close enough to you.
