This is how you throw a curveball: first and second fingers on top of baseball on right seam. The trick to making a curveball spin and drop is the way you throw it. A curveball can be very dangerous to a persons wrist so do not throw a curveball unless you throw it correctly. A curveball is thrown with your wrist cocked to the side so your palm faces sideways.

This is how you throw a Four-seam Fastball: thumb directly under first and second fingers which are spread across the horseshoe if the ball. Throw it like your playing catch. The four-seam fastball is the fastest pitch a pitcher can have. It is also the straightest.