Pitching instructions on the split-fingered fastball 

Tip #1 - Don't throw it until you're old enough
The split-fingered fastball is a pitch that should only be thrown by mature-bodied men, in most cases post high-school aged players 18 years of age or older. It is not a pitch that needs to be learned at a young age, and is only recommended for pitchers with above-average physical arm strength.

Tip #2 - How to grip it
The split-fingered fastball is held as it sounds, by spreading the fingers more than the fastball grip. This will create less spin off the finger tips and allow the sinking action. The fingers are placed outside the seams on a two-seamed fastball.

Tip #3 - When to throw it
The split-fingered fastball is a pitch used to get hitters out by deception of two factors: speed and downward break. Since it has fastball-type velocity, it can get in deep on hitters, but also has late vertical break. Many hitters will chase this type of pitch with two strikes, and it is a power pitch that is used as a strike out pitch: (example 1-2 or 2-2 counts). Many power pitchers use this pitch very effectively.

Tip #4 - Throw it low
This is a difficult pitch to control. Most pitchers cannot or will not throw this pitch for a called strike because of the inconsistency of its break, or because of fear of leaving it up in the strike zone. Thus it's effectiveness, when a hitter has two strikes, and this pitch is thrown low enough.

Tip #5 - Watch the stress
The downside is the stress created on the split-finger tendons up the arm to forearm area.

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