The sketchbook is my first stop after I gather all my reference material. I like to take screenshots from DVDS and Instant Netflix. Adam West's Batman was always my favorite interpretation of the character. Here's Bruce Wayne and Joker, stripped down to lines and shadows (and smart lapels).
It's handy, with reference material, to make collage sketches. The guy in the front is a zombie from "Night of the Living Dead," and the girl on the building in the background is from a magazine. The cinematic posing is already there, which makes it easier for me to play around with my own quick sketch compositions.
J.B. Fletcher, from Murder, She Wrote, is my muse. Here she is solving a murder, sipping a Long Island iced tea. I draw her a lot.
The Sartorialist and similar fashion-on-the-streets sites are great reference sources for just drawing real-life characters with interesting, often layered and textural, wardrobes.