Ok, so here is a quick and dirty tutorial of sorts on how I created the hip joints from wooden balls. The other joints will also be made in a similar way, though their channels will change depending on which joint it is. I haven't made any other joints yet, but I can post pics of them when I do. So, let's get started.....
This is pretty self explanatory.....though I guess I could add that you can get wooden balls at any craft store, and some of them may come with a hole already drilled through it. I would recommend buying the ones with holes drilled into them whenever you can as it saves time and error!
OK, so after you have your ball, you need to get out a ruler, and measure and mark the center with crosshairs. Feel free to make your crosshairs long, as it will help out later on. After you have your center marked you need to drill a hold straight through the ball. My dad has a drill press, so he helped me use that, but you can also do this with a handheld drill I imagine, though you'll need a vise to hold it in place.
So, next you need to mark the front face of your ball joint with centered crosshairs just like you did on top. You will take it back to the drill press again, BUT, you should use a smaller drill bit this time, AND you only want to drill halfway through to where you already drilled and stop. As you can see in my example with my failed joint, my drill was a little off, and we also tried making little drill holes to perforate a channel that would be dremeled out later, however that turned out to be a very bad and messy way to go about things, and I would not recommend doing it that way! If you do decide to perforate I'd only do two additional holes.
What I ended up doing, was putting my ball joint in a vise, as illustrated above, and using my extra long crosshairs as a guide, I took the dremel and made a shallow channel from the top hole to the side hole. After I had a decent channel going I switch to a heftier drill bit and basically drilled out that whole channel you see there.
These are the drill bits I used. I started with the one on the left, and finished with the one on the right. Also this wasn't a terribly fast process. It took me a while to dremel the channel, so don't get discouraged if you think it's taking too long.
Well, that's it, I hope it's helpful!
EDIT: I forgot to mention that it is a little easier if you take out a hand saw, and saw the channel line a little bit before you dremel. The saw line really helps guide the dremel in the beginning