If you want to work with a modeling agency, then you have to take yourself and the photos you present seriously. The first thing to do is go to the website of the agency you want to work with and check out the photos the models have. And then it comes down to producing a photo that is similar which you can submit.
Shorter girls, girls who are not 5'7" should be sticking to commercial print modeling.
It is important to represent yourself clearly and honestly and naturally for commercial print modeling.
I think a lot of girls miss this. They forget importance of perfecting a headshot and beauty shot and they focus too much on flaunting themselves on the web or in wrong ways with wrong photos when a good headshot, that shows your personality and that you have good energy can get you a modeling agency quicker. Models don't just work in the modeling business they work in the advertising business and you have to show in your photos that you can model a product and represent a brand, or product's image.
Watch some commercials, it isn't hard to tell the type of appeal you need because most of the girls in commercials are NOT fashion models.