I separated my ball joints thusly:
1) Make sure you're on stable jackstands.
2) Remove wheel, brake caliper and rotor, etc. (whatever'* all in the way).
3) Remove sway bar endlink.
4) Remove cotter and crown completely.
5) Bang a bit on the sides and bottom of the control arm in the vicinity of the ball joint with a regular old hammer, just to loosen things up a bit.
6) Put the tip of a very large flatblade screwdriver on the control arm, just to the outside of the ball joint; hold screwdriver vertically, perpendicular to control arm.
7) Bang straight down on the back of the handle of the screwdriver with the hammer--hard--until the ball joint pops free.
(I suppose a dull cold chisel, railroad spike, etc. could be used instead of the screwdriver)
2004 Buick Lesabre Limited, Gran Touring; Bone Stock
1998 Buick Lesabre Limited, Gran Touring; Mods: Poly sway bushings/endlinks, Tru-Cool trans cooler, Thrasher shift kit (med), PLIM, front PEM; Mods in progress: Alot of stuff, but slowly...