Lots of flux, a chisel tip iron, solder sucker, and quality desoldering braid.
Start by flowing an excess of fresh solder onto the joint you're trying to de-solder. Old solder is a pain to do anything with, so wetting the joint thoroughly with fresh lead solder is an important first step.
Next, use the solder sucker to remove as much of the excess solder as you can.
Finally, daub a bunch of Rosin based flux onto the joint and the braid. Apply the braid and the iron, and the braid should absorb the rest of the solder.
I've used this technique for many years, and it works even with multi later boards, as good wick will suck the joint completely dry.
Edit: Make your iron just hot enough to melt the solder, so that your flux doesn't boil away too quickly. More heat isn't necessarily good in this situation.
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