I would start with a budget month by month.

Start with your monthly income at the top and then start deducting your expenses line by line (rent, lights, food, gas, car, etc).

Likely there will be a negative number at the bottom. Start going up the sheet of paper and see what can be eliminated (cable TV?, sell car?, eating out?) and what can be reduced (premium cable, data plan on cell phone, designer clothes).

Find ways to increase your income (2nd job, tutoring?, cut grass, book keeping)

You have to learn to live with in your means. Period. If you can't make ends meet with an internship, you are going to have to get a second job.