There is no "proper" way to set this. That's the beauty of it, it's adjustable to each driver. You can have it downshift at part throttle, or wide open, or anywhere in between. The closer you have the slotted rod to the front of the car, the sooner it will downshift. My personal preference is to kick down as soon as possible. You just want to make sure that it does not interfere with wide open throttle.