One word - Don't.
Cutting springs ruins them. The springs are made with formed ends that match the spring isolators & provide an even seating for the spring to its mount. Once a spring is cut, it will never seat correctly.
Not only that, but it messes up the rate at which the spring extends & compresses. The extension & compression rates are engineered into the suspension to keep the car on the road, going in the direction you point it.