I’m 13 years old and I am wondering how I can become a better pitcher. I throw 75 mph with a circle change in the making and a decent curveball. How can I become a better pitcher.
Just wondering…how big are you and how long of mounds do you pitch from?
GO CUBBIES!!! 
Hit corners, change speed, movement on your pitches, deceptiveness. A lot of these will come with experience and a lot of practice but if you can get a video up of your mechanics it could help a lot.
http://www.thecompletepitcher.com/pitching_articles/complete_pitcher.htm
http://www.thecompletepitcher.com/pitching_drills.htm
Those might help.
How the heck do u throw 75??? I can barely hit 60 but I have a beast 12-6 curveball. what do u do!!?