Choosing a background for this piece is critical to the overall feel – you could choose anything from an urban landscape to a warehouse conversion, and each would mean you ended up in a wildly different creative place. The woodland image I’ve used here is a free download from Stock.xchng – you can download it from bit.ly/cmdQa6. Paste this onto a new layer behind the floating girl layer. Position the girl to fit with composition of your chosen shot as naturally as possible.
We’re going to make the model interact with the background. Duplicate the girl layer, set the blending mode to Multiply and then using the Eraser tool (E) delete sections to help the shadows fit into the piece. If you delete too much you can always undo, so don’t be timid at this stage.
Next, paint in a shadow below to help root her in the image and prevent her from like she’s floating in space. Use quite a large brush (B) to get an even distribution and then delete parts of this to get the distribution right. Then set this layer to Multiply and change the opacity until it looks correct.
We’re onto the fun bit now: save the image as a .PSD and open it in Illustrator. Draw your basic vectors around the girl – these can be whatever fits into your idea of what this piece will be. Here, we’re going down a generic geometrical system that works well with most backgrounds.