I will take a stab at this... Be aware that I am speaking about "fashion" models ...there are other types of modeling. And I am in the US so this information applies in this country. It could be different in other countries.
1. Requirements: height ... 5''8" to 5'11", dress size ... 6 or under, body type ...very slim with very small hips and breasts, face ... very photogenic, with big, wide set eyes, full lips, high cheekbones, clear skin and perfect teeth, age ... most start in their mid teens and are retired before they reach 25.
2. They need to live where the work is ... and the most fashion work is in New York. Sometimes the best models are sent to Milan, Paris, and other foreign cities for further developement.
3. The only way to make it big in the fashion industry is to get a good agent. This is done my submitting pictures by mail for consideration or better yet, attending all the open calls at the agencies. They usually see aspiring models for a couple of hours each week.
4. Photoshoots for magazine editorials (minimal pay, but important to have in your book), catalogs and ads)ads are the best paying gigs). Sometimes a fashion model might be used in a TV commercial if the client wants a "high fashion" look.
5. The agency finds all the gigs for the models if they are under an exclusive contract. If it's not exclusive, then the model may find jobs on her own and sometimes even book through other agencies, too. There are different contracts .... so it just depends on which the model signed. The good jobs are always through and agency, however ... since the big clients always go through agents.
6. A model just needs to show up on time, usually face clear of any makeup and her hair dry with light product on it. Her job is to make sure she's the correct wieight, kept her skin and hair in good condition ... in other words, her product is her body and it's got to be top notch. The makeup artists, hair artists and stylists will take it from there. Sometimes she needs to bring appropriate shoes and must have the right undregarments, so she should automatically bring her "models bag" with her. She will be instructed in advance, for anything unusual that is needed. All this applies to photoshoots, too.
If I'm missing something, I'm sure someone else with contribute.
