A good rule of thumb is:
Before you cash/deposit your check (actually, try to get Direct Deposit):
Put 10% of your income into savings/money market.
Rent: 1/3 of salary
Then budget accordingly. Only you know yourself.
It really helps to write it all down and calculate it out. MS Excel is good enough to make a chart or budget sheet. That way you can see exactly where your money is going.
Try and contribute the max to your 401K, especially if there is matching. It's basically free money.
Go to
www.bankrate.com and spend some timne browsing there. You can also goto your school's Financial Aid office or Career Center. They'll be more than happy to give you info. Sometimes schools provide free seminars, workshops on finance etc.
Good Luck!