Throw fastballs low and away. Throw first pitch strikes to get ahead in the count. Take a little off the speed of the throws to have more control of your pitches.
Use the four-seam or two-seam grip with the same arm angle and velocity. The two-seamer will sink and have more movement. Add an occasional change-up to keep the hitter guessing. Spend extra time in practice working on a change-up, since it can help to neutralize good hitters in games.
Young players often try to throw as hard as they can - trying to blow the ball past the hitter. It's fun to strike out hitters with the heat, but often it is better to back off a little on the velocity and throw strikes. The pitcher should aim to keep the hitter off-balance and mess up their timing. They can do this with pitch location, movement and changing speed.
Slow it down
An experienced umpire shared this tip:
It's better for a young pitcher to throw 5 miles an hour slower and locate the pitch in the strike zone than to throw high octane balls out of the zone. Mainly throw fastballs low and away. Have a good player at second base to field the weak ground balls.
I was recently coaching a game where a soft throwing 11-year-old lefty kept the pitches low in the strike zone and induced good 12yo hitters into easy ground ball outs. He did this with pitch location, ball movement and changing speed. The hitters where way out in front - hitting the ball weakly off the end of the bat.
First Pitch Strike
In 1995, Greg Maddox gave up only 43 hits out of the 600 times he threw a first-pitch strike to the hitter. You will have success if you throw first pitch strikes down and away. Keep pitching simple.