Big modeling agencies will teach you what they want you to know for the type of work that they want you to do. Just run off and become a super model and don't worry about any of this. For the rest of you, here are some suggestions.
Books, Magazines and other Media
There are always new books coming on the market about modeling and how to be a model. Some I have seen relate only to the top fashion market, some are just gossip books and some have good starting information. Add to this specialty areas, like makeup books, and there is quite a base of knowledge available on modeling. If one wants to learn about the modeling industry all you need to do is take time to read. I have book reviews and a list of modeling related books on the Book page. Can you learn to be a model from just reading a book? Well no, but it will give you some understanding of the industry, what it will take to be a model, and help you avoid some of the scams. I checked with my local library for books on modeling and found they had only nine books and only one of those was published in the last ten years. You may want to start with your school or local library, but you may have to purchase a book to get current information.There are magazine and newspaper articles popping up on modeling all of the time. Most relate to the top level of fashion modeling and being a super model but sometimes other things will slip through. These articles do not teach you the how-to of modeling. They do, however, give some insight into the industry. I understand there are programs on cable TV about the modeling world. I have seen references to these shows and comments that they give some good insight into the world of fashion modeling. Sorry, I have not seen them. My MTV was 15 years ago.
Web Sites
I have found a lot of web sites on the net either have bad info or have hidden agendas (scams) behind them. There are a few sites that do have good information and will give you another perspective on becoming a model.
Experience
The number one teacher in this business is doing. Once you have been through a photo shoot things start to make more sense. And as you work with other professionals you can learn from them. But getting photo shoots when you are starting out can be hard to impossible. If a photographer has a job, he or she won't want to risk it on a wannabe model. And if you can't find a photographer to do test shoots, you may be left out. If you have to pay for shoots, that can truly be expensive and with no guarantee of ever earning your money back. Hopefully, a good agency can find test shoots, shoot where they want a new face or shoots where they want a less expensive model for you. Getting shoots, gaining experience and building your portfolio are the greatest challenges a new model faces.