Since this achievement can be gained on the way to a perfect game, it's best to shoot for this at the same time. Before you start playing the game, go to the options and make sure the following settings are correct:
- Difficulty: Rookie
- Innings: 9
Select to play a "Pickup Game", set yourself as the "Home" team, and make sure to pick a pitcher with a 5-star Fastball (for me it was Toph from "Avatar"). The rest of the team is at your own discretion.
Pitching is about timing and aiming. Make sure to aim outside of the batter's hotspot area. As for timing, press and hold the "A" button and release either in the green or perfect fill. It doesn't take much to learn the timing.
Since you'll be starting pitching (having picked the "Home" team), simply strike out the first three batters with your fastball. Achievement complete.