Here's a technique I got from Katherine Dewey's book "Creating Lifelike figures in Polymer Clay." (An invaluable resource, by the way. It's out of print,and I had to pay $140 CAN for a copy, but I still consider it a sound investment.)
First, sculpt your head and torso as you would for any project. Use a tapestry needle (or whatever tool is handy) to poke small, deep holes into the torso at the hips and shoulders. Bake the torso long enough that it becomes hard.
Next, make a wire armature for the legs (use trimmed down coat hangers, which are cheap and hold their rigidity wonderfully), anchoring them in the base and the hips with vinyl adhesive, which won't melt as long as you keep the oven on low heat. Sculpt the the legs and arms as normal.
I find this method to be a little more time consuming, but it makes for a very stable figure. You might like to consider it over the soldering wire.