Natural Spines

Separate the torso into three masses: Hip, ripcage, and head. Draw a box or circle for each one when you start the drawing.

Tip the top of the hip forward. Tip the top of the ribcage back. Move the head forward.

You should end up with something like this:

Practice drawing that a few times. Exaggerate the curves that result, and figure out how to add limbs to that in a way that looks right. You should be able to bang out a few of these in 30 seconds and throw on some stick arms and legs in various positions. From there, you can see if the way you drew it works or not. And when you find a way that looks right, practice it a few more times to make sure you've got it.