This week 'Let's make an anime figure' post is a bit late. In the mean time, scoot on over to Matt Bernier's Comic tools blog. What is a blog about comic got to do with sculpting anime figurines? A lot actually.
The key for making a good and believable figure, drawing or sculpture, is an understanding of anatomy. Sure you can learn all the names of the bones and muscles but sometimes you just need a quick reference point. Matt's tutorial on drawing the human figure is great for this. Go to his tutorial and read up on the skeletal system. You can adapt this when you're making your armature. After that go on and read about the muscles. It helped me quite a lot, especially the leg and back muscles. As a starting point, just clik on the link above. It'll bring you his post about constructing the torso part of the skeletal system and then read on from there. Really really good stuff.
So in short, go there and learn some basic anatomy, and I'll post the first part of 'Let's make an anime figure' soon.