I've started work on a new series exploring strong female protagonists in Fairy Tales and Folk Stories (let me know if you know any!) so the girls and I had fun in the studio today getting some action shots. It involved a lot of hamming and karate poses, but we got a few good silhouettes.
Technique: I lit a white backdrop with a single flash unit, had the girls positioned further towards me (and out of the light) and shot with a 60mm lens at f.8. The figures were pretty well silhouetted, but I isolated them in Photoshop and removed any trace of background from around them. I can now drop them into a new layer on 'multiply' to integrate them into an image.