Your lender will usually send semesterly or quarterly payments directly to the school bursar, and then you will typically need to request a refund from the bursar. With the money you get refunded to you, you can take care of books, living expenses et cetera.
Some schools will direct deposit excess student loan funds into your checking account, so that should only take a a couple of days. Others might have more convoluted bureacracy involved?
There is supposedly a lag of a few weeks between when the first semester starts and the first student loan checks arrive, so depending upon your school start date, you might need to cover those first few weeks' expenses out of savings.
In any case, it's not a bad idea to keep a few hundred dollars in reserve just in case you need to spend something before your refund checks or ACH push arrives. On a related note, a lot of schools will provide small (interest free) loans for a short period too to help students get by if they're suddenly in need of a bit of money and the student loan refunds haven't hit their accounts yet.