Front the cutter:
Always stay in front of the cutter.
When O1 pass to O2 the defender jumps to the ball (one pass away).
when O1 starts the cut slides the defender down the court always in front of the cutter.
When O2 pass to O3 the defender stays in front of the cutter.
When the cutter cuts to the off-ballside
the defender stays in the middle (this depends of  your own filosofie, maybe your vision is just out off the key) in pistol defense.
pay atention on split vision.
The same when O3 pass back to O2, the defender go into the right stance.
=> ALWAYS SEE BALL AND MAN
When O2 gives the skippass to O1, the defender sprint to O1 does a close out and defends man to man defense.

Front the cutter over the screen

Cut from the pivot to the high post

Cutting from pivot to low post.