If you have unexpected expenses, such as unplanned medical or dental emergencies not covered by insurance, etc., talk with your financial aid counselor to see if you qualify for a budget increase. If you cannot do this successfully yourself, consider purchasing the latest personal finance software to aid you in keeping track of your spending. Use savings beyond what you need for emergencies to avoid credit card use and limit non-subsidized student loan debt. Have only one credit card with a low maximum balance, and pay your balance in full each month. Don't use credit cards for cash advances.
Most banks charge higher interest on cash advances than for regular purchases.
Keep a record of your monthly credit card purchases on a Post-it note in your checkbook, and subtract that amount from your checking account balance so that you will have it available when you receive the bill.