I start by sculpting a clay figure to drape.
My Method to Create Original Cloth Doll Patterns
Next, I carve deep groves in the torso where I think that I want to make the seams. 
I use my thumb nail and press muslin down into the groves.  I use a water based clay that is leather hard. 
Next, use a ball point pin to mark the sections that will form the pattern pieces. Note that the fabric is smoothed down and that it is apparent that a dart will be needed at the bust.  Mark the fabric with all these details. 
Do this for the front and back of the torso.  On this doll, there are two front pieces on each side of the front and one on each back side.  So, she has 4 front panels and 2 back panels.  DON'T FORGET TO ADD SEAM ALLOWANCES to each piece!
Now, prepare to be shocked!  This slim torso turned into this when stuffed!  Cloth just has a mind of its own.  It stretches on and on!
So, you guessed it, experiment, experiment, experiment.
The original pattern ends up being changed a lot.
This is fairly close the final pattern.
This is the final torso.
I just had to show you her feet!  I love her shoes
made with her legs.  They have hard heels and
she stands alone without a stand. 
I hope this helps you get some ideas!