I think basically everyone here has posted the perfect tutorial for the average beginner, heres an indepth description of what each joint does
Neck: Extends (sticks out) or Contracts (pulls in)
Pecs: Extend (swings arms back) or contracts (swings arms in like you would hand something to someone palms back)
Shoulders: Lowers (swings arms down) or raises (swings arms up)
Elbows: Extends (does basically nothing when arms are straight, just swings elbows out a little) and contracts (swings elbows in as if to pound chest)
Wrists: Extends (view elbow description) and contracts (same thing as elbows, swings hands in)
Chest: Rotates right (swings body to right) or left (swings body to left)
Lumbar: Bends right (tilts to right like arm stretches) or left (tilts left)
Abs: Extends (swings torso back) or contracts (swings torso forwards)
Glutes: Extends (swings leg out) or contracts (pulls them in)
Hips: Extend (swings leg back) or contracts (swings leg forwards)
Knees: Extends (same as elbows, doesnt do much except swing out a tiny bit unless contracted, which then swings out far) or contracts (bends leg in like a crane position in tae kwon do)
Ankles: Extends (bends foot down) or contracts (bends foot up)
All above joints also have
Hold: Firmly locks joint in position, easier for someone to fracture this joint and render it useless in Multiplayer.
and Relax: Leaves joint limp, easier to dismember but harder to fracture. When limp, the joint will be subject to gravty and sort of turn into a ragdoll (if you were pushed, then the joint would swing)
Non-joint parts:
Head: well, just a head
Hands: These can grab the opponent, very useful in fractures.
Other Limbs: Separate the joints and make the body look real
Feet: Can bend joints forcefully
Try to put this into a combination and have some fun!