IMPORTANT : C.A.F. is a French organism devoted to help families, students and people in general. As a student you have right to receive an economical help (I do not know the exact amount, but it may be something like 30 euro/month up to 300 euros/month, depending on your situation and on your accommodation fees).
Warning : you have to go to the CAF's offices as soon as you can (maybe also contact them by telephone as soon as possible) because the payment starts one month AFTER the acceptation of your demand by the offices of the CAF.
CAF will ask you to provide a certain number of papers, as a proof that you are really a French student, so you may be conducted to come back to their offices several times. Be very honest with them about your economical sources, because declaring 0 euro/month implies that they will give you no money at all. It may seem stupid, but it is actually not believable that a student declares no money.
Several operations can be done online since now in their internet site http://www.caf.fr/. You have to open an account and do the necessary operations. Again, everything is in French.