{I didn't make this, unfortunately, but it's too funny not to share}
1. Lighting: harsh. So harsh that your face looks white as a blank dry erase board, onto which teenage girls can write their deepest fears and craziest fantasies, all of which you will fulfill because, duh, you're a vampire. You're basically walking, pasty magic.
2. Gaze: menacing, yet seductive. Look, we all know why you're here: to scare girls into puberty. And the right look from your freakishly light vampire eyes can do just that. Vampires are the ideal teen pin-up because they're dangerous, yet sexually non-threatening. After all, vampires don't want to have sex (which would make pre-teen girls uncomfortable), they just want to drink blood, and possibly turn someone into their eternal vampire bride, which is way, way romantic.
3. Never underestimate the power of a forceful grip. For a normal guy, lurking behind a girl and gripping her upper arm would read "Date rape imminent." But you're a vampire: people expect that kind of creepy controlling behavior from you.
4. Hair: Gelled to perfection. Clothes: Abercrombie casual. The second most important word in your vampire pin-up job description is "pin-up." Without the hair gel, how will anyone know you're supposed to be an object of desire?
5. When everything's in place, have yourself photoshopped in next to a totally uninterested teen girl. Now you're ready for vampire heartthrobhood!
I'm not very familiar with Twilight, the movie or the YA book series, but this poster proves they know their audience. It's like the cover of Dracula BOP! magazine.