The Basics

There are 26+ pieces needed to be sculpted:
1. right/inner calf
2. right/outer calf
3. left /inner calf
4. left/outer calf
5. right/inner thigh
6. right/outer thigh
7. left/inner thigh
8. left/outer thigh
9. groin
10. abdomen
11. chest
12. right sholder

   13. left sholder
14. biceps
15. inner forearm
16. outer forearm
17. helmet
18. back
19. lower back
20. butt
21. right knee cap
22. left knee cap
23. utility belt
24. hand guards
25. shoulder straps
26. Oxygen Cannister
First thing you will need to do is buy a huge load of plasticine clay. I recommend buying a minimum of 50 pounds. Get this from a clay dealer, hobby shop or the manufacturer themselves.... Check your local POTTERY SUPPLY store also.. You can usually get the Oil based plasticine clay for about $1.30 - $1.90 per pound. 50 lbs. of clay will run anywhere from $75.00 to $200.00 depending on where you buy it. Look for the best deal.
Once you have the clay you will need to kneed the clay to make it pliable. ...The clay will soften with heat. When you kneed it you are actually warming it up. You could pop it in the microwave on a LOW temperature for a few seconds to warm it up.

Plasticine uses oils instead of water, but also uses micro-crystaline wax. The wax is what causes it you soften as it is warmed up. you can speed the softening process by putting a block of clay in a microwave. Don't use a high power level, or heat it for long. It will heat up fast, and if over heated, will break down some of the ingrediants. Particularly, it will drive the sulfer out. If this happens, let it cool, and see if it is still usable. DONT touch it, it will burn you very badly.

You can also clean your clay by using heat. Once you have used it, and it has started to get bits of plaster in it, heat it in a double boiler. You will then be able to pour it through a sieve, and get the bits of plaster out. If you are sculpting small details, and the clay is soft and moves around a bit, stick it in the freezer for a little while. It will be much easier to do small details when it is cold and hard. (Thanks to 'Critter Creations' in Texas for this information about plasticine!!!)
Once you get it pliable ... Lay it out into One inch thick slabs .... either smoosh it in to 1 in. thick slabs or roll it into 1 in. slabs... doesn't matter to me. Now... Lets start off with the legs....
You can easily cut slabs of clay by making a "Cutting Board" out of wood and cutting the clay by sliding a piece of wire across the raised rails.
I highly recommend you to take some time and check out the sculpting tutorials at Dan Perez's Workshop. He goes over the finer aspects of clay sculpting and the tools used.