One of the awesome traps that these agencies spring onto clients is the arrangement of payment for a modelling "job". The agency will ensure that it gets paid, but does not give a hoot about the model getting paid, and usually states in the contract that it is the models responsibility to ensure that payment is received for work done. This is not on.
What happens is that the people hiring the models are lead to believe that the agency fee is the only fee to be paid, and then are shocked when 12 models are banging on their doors demanding payment.
If you have a lawyer, get one to look over the contract before signing it.
But, in general, if you do not understand any part of any contract, don't sign it until you do, and even then, sleep on it before you sign.
Pay attention to how business is to be done, how money is to change hands, and try to think of "what would happen if" scenario's and then see what the contract says about that scenario.
e.g. If the model cannot make it to a modelling "job" because the agency did not contact the model in time, does the model have any liability?
e.g. If the model signs with another agency, does the existing agency have any claim to the work?
Here's some good tips on spotting the fake modelling agencies:
http://www.fraudguides.com/modeling_agency_scam.asp
One of the most obvious give-aways that an agency is rubbish is if they want the money in cash.
Take your time, spend some time googling for : modelling agency contract warning.
Be careful, but, have fun.