Well, This is basically just click the enemy and quickly click behind you after the projectile is fired. If you click away to early, the projectile won't fire (attack speed makes this easier to avoid) and clicking too late causes idle standing time.
If you play a particular champion a lot, you'll get a good feel for when the projectile is launched, and can Kite better.
Kalista is an excellent example of how this works, but in a different way. Instead of cancelling the attack, you can just choose where to leap. So, while Orb Walking is impossible on her, she can still make up the distance with her leap. This can help you get in the cadence of clicking an enemy and clicking where you want to go in a short window of time. Ashe is also a good example of learning how to Kite, simply because she slows the enemy on basic attacks.