A way that worked well for me using only a jack and a chain:
Put a floor jack that is already raised about 6 inches under the lower control arm. Wrap a chain UNDER the jack and OVER the upper control arm near the frame. Remove the inner bolts of the lower control arm, not the ball joint nut. Slowly let the jack down.
This way, the pressure was taken off the spring slowly by the hydraulic resistance of the jack and you don't get any sudden surpises. If you don't use the chain, the springs may lift up the car instead of push down the jack (especially with the engine removed). Also, by removing the inner bolts rather than the ball joint nut at first, the arm drops almost straight down rather than swinging down at an angle which can cause the spring to bind or fly out sideways.
This method also works well in reverse when putting the new springs in.
Just one of many techniques!