I was negotiating a modeling gig recently, and thinking about how nude models, and the photographers who shoot them, sort themselves into certain categories and set up little rules.
First, there is figure modeling. This is the serious high-art crowd. The photographer shoots you in black and white and hopes to hang you in an art gallery. In figure modeling, you don't wear any clothes whatsoever, you don't look at the camera, and you definitely don't smile. Photographers don't want you to look too sexy--the turn-on here is supposed to be mental. I like doing figure work, but most photographers don't make any money off it, so they can't afford to pay very well.
Next is glamour modeling, which occupies the vague and sometimes uneasy territory that lies between being an artist's muse and being a porn star. It ranges from almost-naked sexy photos all the way to what are referred to as "Playboy-style nudes"--meaning: completely naked, but no open legs. Glamour models get very testy with anyone who suggests that they spread their legs.
Glamour modeling is demanding because it's sexy, it's definitely commercial, and yet it's not porn--not quite. It's the sizzle without the steak, so by God you better be one sizzling hot babe. The pay is all right, and you do get some pretty pictures of yourself. But doing the no-carb crash diet for five days before the shoot is a bitch, and my dermatologist scolds me about the obligatory pre-shoot tanning-bed session.
Then there's porn modeling, defined as "any pictures people are supposed to be 18 before they look at." Even for doing relatively mild "single-girl" shoots, porn's pay scale is the best. But the aesthetic production values at a porn shoot aren't always high, which is why my porn modeling adventures are infrequent. Since this is a paying hobby rather than a job, I only work for photographers who are going to make me look good.
Modeling for people is kinda like playing with them: The more information you have about what they want, the more likely it is that you can give it to them. But it can be a lot of fun when a photographer says, "Okay, show me what you think is sexy," and then shoots that. Some of the best shoots I've ever done have started that way. I'm a lot sexier playing by my rules rather than someone else's.