This first one is a rough to get the feel of the overall shape of the figure. I establish the simplest outside edges first, and then carve out the negative spaces (such as where her legs part), like cutting into a pie.
I did this next one to give myself an idea of what the main lines would look like. As you can see, her feet didn't line up at first. I later decided that it would look better if the toes of both her feet all followed the same arc (which you can see in the diagram of the final version at the left).
Here's my first attempt at her head, followed by the version I ended up with, in which I tried to make her look less "Sabrina" and more mischievous.
Here are a couple of hat designs. Chuck Jones's original design was more cartoony, so he got away with placing the hat on her head like a coin on an egg, but since my version is slightly more realistic, I had to figure out a sensible way to fit her hat onto the dome of her skull, without intruding on her bangs or ponytail.
And here's the rough of my Viveca Lindfors portrait. (I didn't end up doing a rough for the Lisbeth Salander portrait. The final versions of realistic portraits take longer than the finals of cartoon drawings, so I don't always have time to mess around with roughs beforehand.) In this rough, I'm getting a feel for the three-dimensional shape of her head, and the shadow pattern.
And that's that!