Go to Autozone and borrow their Pitman arm puller if you want to reuse the ball joints, if not borrow the pickel fork and beat them off. I used the Pitman arm puller and it worked like a champ. They charge you the cost of the tool to borrow, but credit you the full amount when you bring it back.
If you do not have access to the puller and wish to reuse the ball joints, a sharp blow to side the spindle mount (at the point where the BJ stud and spindle connect. The point is not to beat the spindle. The stud is tapered and so is the spindle hole. One sharp blow with a metal 1.5lb or 2.0lb hammer will most times "pop it out.
I seen a web site this week where the person made his own ball joint removal tool with a coupler used to mate two threaded rod together. He measured the distance between the studs on the ball joints and took two bolts and the coupler nut and made them the same distance. Then loosened whatever ball joint he wanted to remove and used the setup to push against the stud of the ball joint, I'm sure a slight tap would help matters along.
I've had the best luck with what 66-72 said. The key is to use a big hammer and the SIDE of the spindle. What you are doing is slightly distorting the hole so the joint can pop loose. It often takes a few good whacks, but since you're just hitting cast iron there's little chance of hurting anything. If you beat on the joint itself, you'll just destroy the threads. A "pickle fork" works fine if you are going to replace the balljoint anyway. They tend to destroy the boot and damage the joint itself as well.
I've seen the pullers but in 20 years of mechanic work have yet to ever use one. Or need one.