Step 2: Time to build an armature
First off you will need "armature wire". Most art stores will carry small and large quanities of it. It's basically wire, usually aluminum or steel. You can use paperclips, coat hankers, any metal wire in which you can bend with your fingers and holds up pretty well. Only need a about a foot of it.
What wire am I using?
Wire as you know comes in different gauges. For this demonstration I'm using stuff I found in my dad's tool cabinet.
I found copper wire at 16 gauge and I also found 24 gauge steel wire. An example of a "wire" not to use is soldering wire. It's lead and very weak, it wouldn't hold up for long. Alternatively wire so strong where you couldn't bend it at all with your fingers wouldnt work either. You can use pliers to bend your armature but I like the freedom of bending at will and the ease of it. Work with whatever you like best. You will also need wire cutters. The one's pictured are not really right for the job. Ask a Homer at Home Depot. Probably a good tool to have around anyhow.
Tricks of the trade
Most of the professional sculptors will use two different gauge wires. One thicker wire to build the base armature and a second thinner wire to wrap around the thicker base armature. This will provide a better grip for the clay you will eventually squish around it. Without that second thinner wire the clay tends to slide off.
Measuring, proportions and posing
With this knowledge you're ready to build your figures armature.
Be sure to check the size of your action figure bubble. You want your figure to eventually fit inside the bubble don't you?
You can also use the original action figure as something to measure up to. You will have to decide if you want a certain pose. This being my first attempt at this will keep it real simple. Also instead of building the figure all at once. You might decide it would be easier to build different limbs and torsos sepearate later gluing them together. Also if you do wish to make action figure posable. IE has articulation it will require some more research into jointed limbs. The classic 4 and a half inch GI Joes always had hinges molded into the arm with a rivet to hold them together. You might decide you can use magnets. Or just a metal tube with a rod.