Disclaimer: Much of this is a matter of opinion; as a photographer this is what I want in a model.
1. Know your limitations. Not everyone was meant to be a model. The average height of a model is
5" 6'. Many people don't have the body type for modeling. Do some research and ask around to make sure you have the physical appearance that is desirable for a model.
2. Model, of course, shouldn't be anorexic or do anything unhealthy to keep them in skinny, but if you want to be a model, then you need to take care of your body. No career is worth sacrificing your health for. A lot of models who aren't overly-skinny are considered plus-sized models.I scoff at this term due to the fact that many of them are still slimmer than the average person. Plus-sized modeling is a growing field. As society realized how flawed the portrait of beauty they've created is, some have started trying to fix their mistakes. If you're on the curvy side, plus-sized modeling might be for you.
3. Listen to your photographer. A lot of models have their own ideas of photos they'd like to create. If this is the case with you, talk to your photographer. A lot of times we're happy to oblige. However, I told you that to tell you this: Always listen to what your photographer wants. You work for them, not for your own pleasure.
4. Have confidence. If you don't have confidence the lack thereof will show through into the photographs. You are unable to preform to the best of your abilities, if you don't understand your skills. A model needs to be willing to do unusual, unique poses and show off her attitude in a shoot. If you're overly shy, or unwilling to think outside the box this makes you incredibly less desirable.
5. Make suggestions, but don't demand. This applies to the styling, make up artistry and photography itself. Don't tell the make up artist "that's not my color" or "I look weird"; they know what they're doing. They've been trained to make you look your best. Stylists, admittedly, can do a pretty kinky job, but once again, this is their job, not yours. Your job is to stand there and pose. As before stated, suggestions to the photographer are, in most cases, acceptable. Don't let the photographer how you "have to pose" to look good. Sure, sometimes we flop and make your ankle look bigger than your head, but we still know better than you. Seriously, trust the people taking care of the shoot.
6. Act. The best way to create the best look for the shoot you're doing is to find out what you'll be doing ahead of time. Think over the mood of the scene and practice letting your face convey that mood in a mirror. When you get to the shoot you'll be able to make a much more satisfying product.
7. Loosen up and have fun with the photographer. This doesn't mean you should smile the whole time, it just means you should be able to enjoy your time shooting. Don't be nervous or self-conscious. Remember that you wouldn't be a model if you didn't deserve it.
8. Do not EVER complain to the photographer about editing. They know how to create amazing images; just step back and watch the magic. Don't tell the photographer not to use a picture just because you don't like it. It's not their property and they have the right to do whatever they please with it.