When ripe, pistachio shells will naturally open on their own. Roasting processes will also open the nut. Because of this, pistachio nuts are typically the easiest nut to crack open. They do not require nut crackers or hammers, just your fingers. Sometimes they can be difficult to crack open, however, if the shell is not already mostly open.
Cracking a Pistachio Shell
Hold the pistachio in your fingers with the pointed end facing up.
Place your two thumbs on either side of the shell, where it is open at the top.
Pull the shell open, releasing the pistachio nut inside.
Cracking a Partially Open Shell
Place the partially opened nut on its side on a table or plate.
Place the pointed end of another pistachio nut into the small slit in the partially opened pistachio.
Twist the nut clockwise, then counter-clockwise, making the crack bigger in the process.
Pull the shell pieces apart once the crack has gotten large enough to grab with your fingers.